Fixed a minor cmake problem, occuring when DYNAMIC_CORE=ON and CMAKE_C_FLAGS was empty

Author: k.dunikowski

cmake/arch.cmake

@@ -73,7 +73,7 @@ if (DYNAMIC_ARCH)
     endif ()
     if (NOT NO_AVX512)
       set(DYNAMIC_CORE ${DYNAMIC_CORE} SKYLAKEX)
-      string(REGEX REPLACE "-march=native" "" CMAKE_C_FLAGS ${CMAKE_C_FLAGS})
+      string(REGEX REPLACE "-march=native" "" CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
    endif ()
     if (DYNAMIC_LIST)
 	set(DYNAMIC_CORE PRESCOTT ${DYNAMIC_LIST})