Teach CMAKE_DETERMINE_COMPILER_ID to check for variable
CMAKE_${lang}_COMPILER_ID_TOOL after CMAKE_DETERMINE_COMPILER_ID_BUILD
to use as CMAKE_${lang}_COMPILER since it will not be known until after
the IDE runs.

In CMAKE_DETERMINE_COMPILER_ID_BUILD prepare a cascading "if" so we can
use a generator-specific method to compile the identification source
file.  Leave "if(0)" as a placeholder for now and put the direct
compiler invocation in "else()".  After running the compiler to build
the compiler identification source we file(GLOB) the list of output
files as candidates for extracting the compiler information.  An IDE may
create directories, so exclude exclude directories from this list.