[libc] Link mpfr and gmp wrapper to the libcMPFRWrapper.

This will fix building the wrapper shared library when
BUILD_SHARED_LIBS is ON.

Reviewers: PaulkaToast

Differential Revision: https://reviews.llvm.org/D78737

GitOrigin-RevId: 1e2772c0a3333f10b3fd0e0220022e80f4b0afd2
1 file changed