astro/opencpn: fix build on powerpc64 elfv2
For some reason SSE support is misdetected on by clang:
- Probing for compiler -msse support -- OK
- Probing for compiler -msse2 support -- OK
- Probing for compiler -msse3 support -- OK
- Probing for compiler -mavx2 support -- OK
Later:
In file included from /wrkdirs/usr/ports/astro/opencpn/work/OpenCPN-5.2.0/libs/texcmp/squish/clusterfit.cpp:27:
In file included from /wrkdirs/usr/ports/astro/opencpn/work/OpenCPN-5.2.0/libs/texcmp/squish/clusterfit.h:32:
In file included from /wrkdirs/usr/ports/astro/opencpn/work/OpenCPN-5.2.0/libs/texcmp/squish/simd.h:34:
In file included from /wrkdirs/usr/ports/astro/opencpn/work/OpenCPN-5.2.0/libs/texcmp/squish/simd_sse.h:29:
In file included from /usr/lib/clang/11.0.0/include/xmmintrin.h:13:
/usr/lib/clang/11.0.0/include/mmintrin.h:33:5: error: use of undeclared identifier 'builtin_ia32_emms'; did you mean 'builtin_isless'?
__builtin_ia32_emms(); ^