Build with optim flags at link time
When compiling with LTO enabled, the compiler might try to embed some optimisations into the final code.
This apparently doesn't work for arm with neon where the final links yield the following error:
/usr/lib/gcc/armv7hl-redhat-linux-gnueabi/10/include/arm_neon.h:10426:22: fatal error: You must enable NEON instructions (e.g. ‘-mfloat-abi=softfp’ ‘-mfpu=neon’) to use these intrinsics.
While we're here, do the same for sse/avx flags as well just in case.
Fixes: #31 (closed)