The fix for clang in files/patch-src_avtk_avtk_picojson.hxx breaks GCC. Have two versions for two compilers. Fix altivec in src/avtk/libs/pffft.cxx and add -maltivec to CXXFLAGS on powerpc64. Also use new compilers. PR: 239518 Approved by: yuri (maintainer), tcberner (mentor) Differential Revision: https://reviews.freebsd.org/D21141