ENH: merge CMake-CrossCompileBasic to HEAD

-add a RESULT_VARIABLE to INCLUDE()
-add CMAKE_TOOLCHAIN_FILE for specifiying your (potentially crosscompiling) toolchain
-have TRY_RUN() complain if you try to use it in crosscompiling mode (which were compiled but cannot run on this system)
-use CMAKE_EXECUTABLE_SUFFIX in TRY_RUN(), probably TRY_RUN won't be able to
run the executables if they have a different suffix because they are
probably crosscompiled, but nevertheless it should be able to find them
-make several cmake variables presettable by the user: CMAKE_C/CXX_COMPILER, CMAKE_C/CXX_OUTPUT_EXTENSION, CMAKE_SYSTEM_NAME, CMAKE_SYSTEM_INFO_FILE
-support prefix for GNU toolchains (arm-elf-gcc, arm-elf-ar, arm-elf-strip etc.)
-move ranlib on OSX from the file command to a command in executed in cmake_install.cmake
-add support for stripping during install in cmake_install.cmake
-split out cl.cmake from Windows-cl.cmake, first (very incomplete) step to support MS crosscompiling tools
-remove stdio.h from the simple C program which checks if the compiler works, since this may not exist for some embedded platforms
-create a new CMakeFindBinUtils.cmake which collects the search fro ar, ranlib, strip, ld, link, install_name_tool and other tools like these
-add support for CMAKE_FIND_ROOT_PATH for all FIND_XXX commands, which is a
list of directories which will be prepended to all search directories, right
now as a cmake variable, turning it into a global cmake property may need
some more work
-remove cmTestTestHandler::TryExecutable(), it's unused
-split cmFileCommand::HandleInstall() into slightly smaller functions

Alex

Source/cmIncludeCommand.h

@@ -68,12 +68,14 @@ public:
   virtual const char* GetFullDocumentation()
     {
     return
-      "  INCLUDE(file1 [OPTIONAL])\n"
-      "  INCLUDE(module [OPTIONAL])\n"
+      "  INCLUDE(file1 [OPTIONAL] [RESULT_VARIABLE <VAR>])\n"
+      "  INCLUDE(module [OPTIONAL] [RESULT_VARIABLE <VAR>])\n"
       "Reads CMake listfile code from the given file.  Commands in the file "
       "are processed immediately as if they were written in place of the "
       "INCLUDE command.  If OPTIONAL is present, then no error "
-      "is raised if the file does not exist.\n"
+      "is raised if the file does not exist.  If RESULT_VARIABLE is given "
+      "the variable will be set to the full filename which "
+      "has been included or NOTFOUND if it failed.\n"
       "If a module is specified instead of a file, the file with name "
       "<modulename>.cmake is searched in the CMAKE_MODULE_PATH.";
     }