FortranCInterface: Fix support for VS with Intel toolset
When using a Visual Studio generator with an Intel toolset, such as
-T "Intel C++ Compiler XE 14.0"
the generated FortranCInterface mangling detection project may fail to
build due to devenv
not working with the /project ALL_BUILD
option.
This seems to be a bug in devenv
or the Intel VS integration. Work
around the problem by building with /project FortranCInterface
instead. We only need to build this executable and its dependencies
within the detection test project anyway.
Fixes: #16519 (closed)