Building with brew on macOS fails

The first problem is that the gcc packet is now gcc-8 and this seems to expects a gcc-7. At least it only looks for gcc-7. After fixing that by symlinking the gcc Cellar to gcc-7 I get this build error:

==> Installing redox-os/gcc_cross_compilers/x86_64-elf-gcc
==> Downloading http://mirror.tochlab.net/pub/gnu/gcc/gcc-7.1.0/gcc-7.1.0.tar.bz2
######################################################################## 100.0%
==> ../configure --disable-nls --target=x86_64-elf --disable-werror --prefix=/usr/local/Cellar/x86_64-elf-gcc/7.1.0 --enable-languages=c,c++ --without-headers --with-gmp=/usr/local/opt/gmp --with-mpfr=/usr/local/opt/mpfr 
==> make all-gcc
Last 15 lines from /Users/alex/Library/Logs/Homebrew/x86_64-elf-gcc/02.make:
                   ^~~~~~~~~~~~~
../../gcc/graphite-optimize-isl.c:57:19: note: suggested alternative: 'isl_aff_dim'
   unsigned dims = isl_space_dim (space, isl_dim_set);
                   ^~~~~~~~~~~~~
                   isl_aff_dim
../../gcc/graphite-optimize-isl.c:60:3: error: 'isl_space_free' was not declared in this scope
   isl_space_free (space);
   ^~~~~~~~~~~~~~
../../gcc/graphite-optimize-isl.c:60:3: note: suggested alternative: 'isl_aff_free'
   isl_space_free (space);
   ^~~~~~~~~~~~~~
   isl_aff_free
make[1]: *** [graphite-optimize-isl.o] Error 1
rm gcc.pod
make: *** [all-gcc] Error 2