This function builds a simple test project using a combination of
Fortran and C (and optionally C++) to verify that the compilers are
compatible. The idea is to help projects report very early to users
that the compilers specified cannot mix languages.
We split the main detection logic into a Detect.cmake support module and
load it only when detection results are not already available. This
allows results computed by the main project to be used in try-compile
projects without recomputing them. The call to try_compile() need only
to pass FortranCInterface_BINARY_DIR through the CMAKE_FLAGS option.