removed -march option in configuration

singularity/debian/singularityfile_debian

@@ -89,7 +89,7 @@ Singularity container for GRASS GIS to be run into GRASS main directory
     cd /tmp/grass_build
     # -O2 -march=native -std=gnu99 -m64
     LDFLAGS="-s"
-    CFLAGS="-O2 -march=x86-64 -std=gnu99 -m64"
+    CFLAGS="-O2 -std=gnu99 -m64"
     CXXFLAGS="-O2"
     GRASS_PYTHON=/usr/bin/python3
     ./configure \