lang/ruby26: fix build on powerpc, don't use GCC on powerpc64 elfv2

ruby currently has issues when compiling on powerpc with gcc9. Use base GCC instead.

Also don't use GCC on powerpc64 elfv2, builds fine with clang.

PR: 242630
Submitted by: nunovasconcellos@gmail.com
Reported by: canardo909@gmx.com
Approved by: portmgr (build fix blanket)