Hack Travis-CI to have MPICH bottle use gcc 6 libs

Author: zbeekman

.travis.yml

@@ -119,10 +119,8 @@ install:
         if ! [[ "$(brew ls --versions mpich)" ]]; then
           brew install --force-bottle mpich
         fi
-        which gfortran || true
-        which gfortran-6 || true
-        which gcc || true
-        which gcc-6 || true
+        rm -rf /usr/local/opt/gcc || true
+        ln -s /usr/local/opt/gcc@6 /usr/local/opt/gcc # hack to get dynamic linker to find gcc 6 stuff
         mpif90 --version || mpif90 -show
         mpicc --version || mpicc -show
         cmake --version