Declare project dependency on C to avoid the CMAKE default of C,C++

[martin-frbg]

Description
#834 had removed all language requirements from the project command in the toplevel CMakeLists.txt in order to move the dependencies on a Fortran compiler to those subprojects that actually need them (and make LAPACKE buildable without one).
However, the default in CMAKE is to assume a project dependency on both C and C++ if no language was
expressly requested. In the absence of any actual C++ code, this creates a spurious dependency that can prevent building
LAPACK on systems where such a compiler is not available or at least not installed by default. (This was noted in a comment on #988)

[martin-frbg]

the two CI errors on Mac appear to be caused by an update of the underlying image "macos-latest" to a version that no longer provides the gcc-11/gfortran-11 named in the build command. At a guess these would be replaced by version 13 or 14

[martin-frbg]

Indeed the "macos-latest" image has been updated from 14.6 to 14.6.1 recently, and following the embedded link in the CI log to the list of installed software in that runner image leads to a message stating that gcc-11 was to be removed from all images on August 12 actions/runner-images#10213