cmake: fix compiler flags filtering

cmake/OpenCVUtils.cmake

@@ -508,7 +508,7 @@ macro(ocv_warnings_disable)
       foreach(var ${_flag_vars})
         foreach(warning ${_gxx_warnings})
           if(NOT warning MATCHES "^-Wno-")
-            string(REGEX REPLACE "${warning}(=[^ ]*)?" "" ${var} "${${var}}")
+            string(REGEX REPLACE "(^|[ ]+)${warning}(=[^ ]*)?([ ]+|$)" " " ${var} "${${var}}")
             string(REPLACE "-W" "-Wno-" warning "${warning}")
           endif()
           ocv_check_flag_support(${var} "${warning}" _varname "")