add notes on building with g++ v9 and v10

Signed-off-by: cmsxbc <i@cmsis.me>

README.md

@@ -80,6 +80,16 @@ benchmark](https://github.com/google/benchmark) frameworks respectively. You
 can configure meson to build them both by using `-Dbuild_tests=true` and
 `-Dbuild_benchmarks=true`.
 
+### Note about building with avx512 by g++ v9 and v10
+
+There is a risk when compile with avx512 by g++ v9 and v10,
+as some `MMX Technology` instructions is used by g++ v9/v10 
+without clearing fpu state. 
+Check [issue 154](https://github.com/intel/x86-simd-sort/issues/154) 
+for more details.
+
+Adding `g++` option `-mno-mmx`, which disables `MMX Technology` instructions, is a possible workaround.
+
 ## Example usage
 
 #### Sort an array of floats