Drop the last use of CMAKE_OSX_SYSROOT_DEFAULT. Replace internal
platform variable CMAKE_${lang}_HAS_ISYSROOT with a more general
CMAKE_${lang}_SYSROOT_FLAG variable. If the -isysroot flag exists and
CMAKE_OSX_SYSROOT points to an SDK (not "/") then always add it to
compiler command lines. This is already done in the Xcode IDE.
The commit "Split GNU compiler information files" broke the settings of
CMAKE_SHARED_LIBRARY_CREATE_${lang}_FLAGS
CMAKE_SHARED_MODULE_CREATE_${lang}_FLAGS
and started using just "-shared" for them. This worked when tested on newer
Mac machines, but older ones really need "-dynamiclib" and "-bundle" (which are
the documented flags anyway).
Previously we checked for this flag by parsing the version number of GCC
out of 'gcc --version', but this is not reliable because the format can
vary greatly. Now we run 'gcc -v --help' and look for '-isysroot' in
the list of options.
We also now store the result on a per-language basis in the per-compiler
info file "CMake<LANG>Compiler.cmake". This is necessary to make it
accessible from try-compile projects so that they generate correctly.
Brad King
David Cole