Rebuild all other GCC packages against mpfr4, so they don't fail with:
Error loading shared library libmpfr.so.4: No such file or directory (needed by /usr/gcc4/libexec/gcc/x86_64-alpine-linux-musl/4.9.2/cc1)
[ci:skip-build]: won't finish in time
Related: 2b32ed3a48786fa151cad8f920e5d9997bee94ed in Alpine's aports.git