Extend the signature
try_compile(RESULT_VAR <bindir> <srcfile> ...)
to allow multiple sources as
try_compile(RESULT_VAR <bindir> SOURCES <srcfile>... ...)
Process the sources to generate a CMakeLists.txt that enables all needed
languages.
Teach the TryCompile test to try cases with two sources of the same
language and of mixed languages. Teach RunCMake.try_compile to cover
error cases for the signature.
Brad King