biology/gcta: Add temporary hack for building on aarch64

Add USE_GCC to work around this issue with clang:

/usr/ports/biology/gcta/work/gcta-1.94.1/submods/plink-ng/2.0/ \

plink2_base.h:1008:23: error: argument to '__builtin_neon_vshrq_n_v' \
must be a constant integer

return R_CAST(VecW, _mm_srli_epi64(R_CAST(__m128i, vv), ct));
/usr/lib/clang/14.0.5/include/arm_neon.h:25260:24: note: expanded from \

macro 'vshrq_n_u64'

ret = (uint64x2_t) builtin_neon_vshrq_n_v((int8x16_t)s0, p1, 51);