While working on reproducible builds for openSUSE, I found that
our ugrep binaries depend on the build machine CPU again.

It seems SR 1166721 reverted my previous SR 818786

related: https://github.com/Genivia/ugrep/pull/50 CPU march=native ; partial
fix


The buildroot diff shows
+++ /home/abuild/rpmbuild/BUILD.unsorted/ugrep-5.1.4/Makefile
@@ -327,9 +327,9 @@
 SED = /usr/bin/sed
 SET_MAKE =
 SHELL = /usr/bin/bash
-SIMD_AVX2_FLAGS = -mavx2
+SIMD_AVX2_FLAGS = 
 SIMD_AVX512BW_FLAGS =
-SIMD_FLAGS = -msse2 -DHAVE_AVX2
+SIMD_FLAGS = -msse2 -DHAVE_SSE2


There are multiple ways to solve that:
- never use AVX2 (as before)
- always use AVX2
- detect AVX2 at runtime instead of compile-time