Your processor doesn't support aes  which is in your CPU_FLAGS_86 and CFLAGS="- march=westmere" Building nettle with aes cpu flag set on gcc when your processor doesn't support aes could be the cause of the error. Reference: https://gcc.gnu.org/onlinedocs/gcc/x86-Options.html   ‘westmere’ Intel Westmere CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AES and PCLMUL instruction set support.   Set to native and add the proper fl