Avoid adding blanket march=skylake-avx512 to dynamic_arch builds

Author: martin-frbg

Makefile.x86_64

@@ -9,6 +9,7 @@ endif
 endif
 
 ifeq ($(CORE), SKYLAKEX)
+ifndef DYNAMIC_ARCH
 ifndef NO_AVX512
 CCOMMON_OPT += -march=skylake-avx512
 FCOMMON_OPT += -march=skylake-avx512
@@ -22,6 +23,7 @@ endif
 endif
 endif
 endif
+endif
 
 ifeq ($(OSNAME), Interix)
 ARFLAGS		= -m x64