Fix FTBFS gcc backend on ppc64*
Tentatively patch gcc on Power for vhdl language. Change d/rules to remove quilt .pc directory after the patch for gcc has been applied, else the gcc build does not apply its gcc patchset, finding a .pc with 1 patch fully applied that is fix_ghdl_ppc64.patch .
I could build ghdl on ppc64 and ppc64el. I manually tried the upstream testsuite : some errors appeared but it doesn't seem to be entirely broken by this.