pts/cpuminer-opt-1.5.1 fails to build with Clang

[marxin]

Fails with CC=clang CXX=clang++ due to:

./simd-utils/simd-64.h:90:10: error: argument to '__builtin_ia32_palignr' must be a constant integer
./simd-utils/simd-128.h:In file included from algo/blake/blake2s-hash-4way.c175:12: error: argument to '__builtin_ia32_insertps128' must be a constant integer
./simd-utils/simd-128.h:179:27: error: argument to '__builtin_ia32_insertps128' must be a constant integer
./simd-utils/simd-64.h:90:10: error: argument to '__builtin_ia32_palignr' must be a constant integer
./simd-utils/simd-128.h:183:12: error: argument to '__builtin_ia32_insertps128' must be a constant integer
...