Syntax fix

cmake/system.cmake

@@ -41,10 +41,12 @@ if (DEFINED BINARY AND DEFINED TARGET AND BINARY EQUAL 32)
   endif ()
 endif ()
 
-if (DEFINED TARGET AND ${TARGET} STREQUAL "SKYLAKEX" AND NOT NO_AVX512)
+if (DEFINED TARGET)
+if (${TARGET} STREQUAL "SKYLAKEX" AND NOT NO_AVX512)
   set (CCOMMON_OPT "${CCOMMON_OPT} -march=skylake-avx512")
   set (FCOMMON_OPT "${FCOMMON_OPT} -march=skylake-avx512")
 endif()
+endif()
 
 if (DEFINED TARGET)
   message(STATUS "Targeting the ${TARGET} architecture.")