Use -dumpversion with gcc only

cmake/system.cmake

@@ -42,15 +42,19 @@ if (DEFINED BINARY AND DEFINED TARGET AND BINARY EQUAL 32)
 endif ()
 
 if (DEFINED TARGET)
-if (${TARGET} STREQUAL "SKYLAKEX" AND NOT NO_AVX512)
-  set (KERNEL_DEFINITIONS "${KERNEL_DEFINITIONS} -march=skylake-avx512")
-endif()
-if (${TARGET} STREQUAL "HASWELL" AND NOT NO_AVX2)
-   execute_process(COMMAND ${CMAKE_C_COMPILER} -dumpversion OUTPUT_VARIABLE GCC_VERSION)
-   if (${GCC_VERSION} VERSION_GREATER 4.7 OR ${GCC_VERSION} VERSION_EQUAL 4.7)
-     set (KERNEL_DEFINITIONS "${KERNEL_DEFINITIONS} -mavx2")
-   endif()
-endif()
+  if (${TARGET} STREQUAL "SKYLAKEX" AND NOT NO_AVX512)
+    set (KERNEL_DEFINITIONS "${KERNEL_DEFINITIONS} -march=skylake-avx512")
+  endif()
+  if (${TARGET} STREQUAL "HASWELL" AND NOT NO_AVX2)
+    if (${CMAKE_C_COMPILER_ID} STREQUAL "GNU")
+      execute_process(COMMAND ${CMAKE_C_COMPILER} -dumpversion OUTPUT_VARIABLE GCC_VERSION)
+      if (${GCC_VERSION} VERSION_GREATER 4.7 OR ${GCC_VERSION} VERSION_EQUAL 4.7)
+        set (KERNEL_DEFINITIONS "${KERNEL_DEFINITIONS} -mavx2")
+      endif()
+    elseif (${CMAKE_C_COMPILER_ID} STREQUAL "CLANG")
+      set (KERNEL_DEFINITIONS "${KERNEL_DEFINITIONS} -mavx2")
+    endif()
+  endif()
 endif()
 
 if (DEFINED TARGET)