UPDATE: This list is getting a little out dated (it was generated with Xcode 4.1). You should run the command suggested by dunedin15.
dunedin15's answer can give inaccurate results for some edge-cases, such as when debugging build settings of a static lib for an Archive build, see Slipp D. Thompson's answer for a more robust output.
Original Answer
Variable Example
PATH "/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin:/Developer/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin"
LANG en_US.US-ASCII
IPHONEOS_DEPLOYMENT_TARGET 4.1
ACTION build
AD_HOC_CODE_SIGNING_ALLOWED NO
ALTERNATE_GROUP staff
ALTERNATE_MODE u+w,go-w,a+rX
ALTERNATE_OWNER username
ALWAYS_SEARCH_USER_PATHS YES
APPLE_INTERNAL_DEVELOPER_DIR /AppleInternal/Developer
APPLE_INTERNAL_DIR /AppleInternal
APPLE_INTERNAL_DOCUMENTATION_DIR /AppleInternal/Documentation
APPLE_INTERNAL_LIBRARY_DIR /AppleInternal/Library
APPLE_INTERNAL_TOOLS /AppleInternal/Developer/Tools
APPLY_RULES_IN_COPY_FILES NO
ARCHS "armv6 armv7"
ARCHS_STANDARD_32_64_BIT "armv6 armv7"
ARCHS_STANDARD_32_BIT "armv6 armv7"
ARCHS_UNIVERSAL_IPHONE_OS armv7
AVAILABLE_PLATFORMS "iphonesimulator macosx iphoneos"
BUILD_COMPONENTS "headers build"
BUILD_DIR "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/BuildProductsPath"
BUILD_ROOT "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/BuildProductsPath"
BUILD_STYLE
BUILD_VARIANTS normal
BUILT_PRODUCTS_DIR "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/BuildProductsPath/Distribution-iphoneos"
CACHE_ROOT /var/folders/2x/rvb2r9s16mq6r318zxvn0lk80000gn/C/com.apple.Xcode.501
CCHROOT /var/folders/2x/rvb2r9s16mq6r318zxvn0lk80000gn/C/com.apple.Xcode.501
CHMOD /bin/chmod
CHOWN /usr/sbin/chown
CLASS_FILE_DIR "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build/JavaClasses"
CLEAN_PRECOMPS YES
CLONE_HEADERS NO
CODESIGNING_FOLDER_PATH "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/InstallationBuildProductsLocation/Applications/project.app"
CODE_SIGNING_ALLOWED YES
CODE_SIGNING_REQUIRED YES
CODE_SIGN_CONTEXT_CLASS XCiPhoneOSCodeSignContext
CODE_SIGN_IDENTITY "iPhone Distribution"
COMBINE_HIDPI_IMAGES NO
COMPOSITE_SDK_DIRS /var/folders/2x/rvb2r9s16mq6r318zxvn0lk80000gn/C/com.apple.Xcode.501/CompositeSDKs
COMPRESS_PNG_FILES YES
CONFIGURATION Distribution
CONFIGURATION_BUILD_DIR "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/BuildProductsPath/Distribution-iphoneos"
CONFIGURATION_TEMP_DIR "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos"
CONTENTS_FOLDER_PATH project.app/Contents
COPYING_PRESERVES_HFS_DATA NO
COPY_PHASE_STRIP YES
COPY_RESOURCES_FROM_STATIC_FRAMEWORKS YES
CP /bin/cp
CURRENT_ARCH armv7
CURRENT_VARIANT normal
DEAD_CODE_STRIPPING YES
DEBUGGING_SYMBOLS YES
DEBUG_INFORMATION_FORMAT dwarf-with-dsym
DEPLOYMENT_LOCATION YES
DEPLOYMENT_POSTPROCESSING YES
DERIVED_FILES_DIR "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build/DerivedSources"
DERIVED_FILE_DIR "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build/DerivedSources"
DERIVED_SOURCES_DIR "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build/DerivedSources"
DEVELOPER_APPLICATIONS_DIR /Developer/Applications
DEVELOPER_BIN_DIR /Developer/usr/bin
DEVELOPER_DIR /Developer
DEVELOPER_FRAMEWORKS_DIR /Developer/Library/Frameworks
DEVELOPER_FRAMEWORKS_DIR_QUOTED ""/Developer/Library/Frameworks""
DEVELOPER_LIBRARY_DIR /Developer/Library
DEVELOPER_SDK_DIR /Developer/SDKs
DEVELOPER_TOOLS_DIR /Developer/Tools
DEVELOPER_USR_DIR /Developer/usr
DEVELOPMENT_LANGUAGE English
DOCUMENTATION_FOLDER_PATH project.app/English.lproj/Documentation
DO_HEADER_SCANNING_IN_JAM NO
DSTROOT "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/InstallationBuildProductsLocation"
DWARF_DSYM_FILE_NAME project.app.dSYM
DWARF_DSYM_FILE_SHOULD_ACCOMPANY_PRODUCT NO
DWARF_DSYM_FOLDER_PATH "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/BuildProductsPath/Distribution-iphoneos"
EFFECTIVE_PLATFORM_NAME -iphoneos
EMBEDDED_PROFILE_NAME embedded.mobileprovision
ENABLE_HEADER_DEPENDENCIES YES
ENABLE_OPENMP_SUPPORT NO
ENTITLEMENTS_ALLOWED YES
ENTITLEMENTS_REQUIRED YES
EXCLUDED_INSTALLSRC_SUBDIRECTORY_PATTERNS ".svn CVS"
EXECUTABLES_FOLDER_PATH project.app/Executables
EXECUTABLE_FOLDER_PATH project.app
EXECUTABLE_NAME project
EXECUTABLE_PATH project.app/project
FILE_LIST "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build/Objects/LinkFileList"
FIXED_FILES_DIR "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build/FixedFiles"
FRAMEWORKS_FOLDER_PATH project.app/Frameworks
FRAMEWORK_FLAG_PREFIX -framework
FRAMEWORK_SEARCH_PATHS ""/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/BuildProductsPath/Distribution-iphoneos" "
FRAMEWORK_VERSION A
FULL_PRODUCT_NAME project.app
GCC3_VERSION 3.3
GCC_C_LANGUAGE_STANDARD gnu99
GCC_INLINES_ARE_PRIVATE_EXTERN YES
GCC_PFE_FILE_C_DIALECTS "c objective-c c++ objective-c++"
GCC_PRECOMPILE_PREFIX_HEADER YES
GCC_PREFIX_HEADER project/Prefix.pch
GCC_PREPROCESSOR_DEFINITIONS "NDEBUG DISTRIBUTION_BUILD=1 KK_TARGET=0x000F0"
GCC_SYMBOLS_PRIVATE_EXTERN YES
GCC_THUMB_SUPPORT YES
GCC_TREAT_WARNINGS_AS_ERRORS NO
GCC_VERSION com.apple.compilers.llvm.clang.1_0
GCC_VERSION_IDENTIFIER com_apple_compilers_llvm_clang_1_0
GCC_WARN_ABOUT_RETURN_TYPE YES
GCC_WARN_UNUSED_FUNCTION YES
GCC_WARN_UNUSED_VARIABLE YES
GENERATE_MASTER_OBJECT_FILE NO
GENERATE_PKGINFO_FILE YES
GENERATE_PROFILING_CODE NO
GID 20
GROUP staff
INPUT_FILE_BASE Default
INPUT_FILE_DIR "/Volumes/Development/Project Game/Project-v1/images"
INPUT_FILE_NAME Default.png
INPUT_FILE_PATH "/Volumes/Development/Project Game/Project-v1/images/Default.png"
SCRIPT_INPUT_FILE "/Volumes/Development/Project Game/Project-v1/images/Default.png"
SCRIPT_OUTPUT_FILE_0 "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build/DerivedSources/Default.png"
EXCLUDED_RECURSIVE_SEARCH_PATH_SUBDIRECTORIES "*.nib *.lproj *.framework *.gch (*) CVS .svn .git *.xcodeproj *.xcode *.pbproj *.pbxproj"
HEADERMAP_INCLUDES_FLAT_ENTRIES_FOR_TARGET_BEING_BUILT YES
HEADERMAP_INCLUDES_FRAMEWORK_ENTRIES_FOR_ALL_PRODUCT_TYPES YES
HEADERMAP_INCLUDES_NONPUBLIC_NONPRIVATE_HEADERS YES
HEADERMAP_INCLUDES_PROJECT_HEADERS YES
HEADER_SEARCH_PATHS ""/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/BuildProductsPath/Distribution-iphoneos/include" "
ICONV /usr/bin/iconv
INFOPLIST_EXPAND_BUILD_SETTINGS YES
INFOPLIST_FILE project/Resources/Info.plist
INFOPLIST_OUTPUT_FORMAT binary
INFOPLIST_PATH project.app/Info.plist
INFOPLIST_PREPROCESS NO
INFOSTRINGS_PATH project.app/English.lproj/InfoPlist.strings
INPUT_FILE_REGION_PATH_COMPONENT
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…