[build] CMake: Make NO_WERROR also work on MSVC (wpilibsuite#7594)

Author: Gold856

cmake/modules/CompileWarnings.cmake

@@ -14,18 +14,20 @@ macro(wpilib_target_warnings target)
 
         target_compile_options(${target} PRIVATE ${WARNING_FLAGS})
     else()
-        target_compile_options(
-            ${target}
-            PRIVATE
-                /wd4146
-                /wd4244
-                /wd4251
-                /wd4267
-                /wd4324
-                /WX
-                /D_CRT_SECURE_NO_WARNINGS
-                ${WPILIB_TARGET_WARNINGS}
+        set(WARNING_FLAGS
+            /wd4146
+            /wd4244
+            /wd4251
+            /wd4267
+            /wd4324
+            /D_CRT_SECURE_NO_WARNINGS
+            ${WPILIB_TARGET_WARNINGS}
         )
+        if(NOT NO_WERROR)
+            set(WARNING_FLAGS ${WARNING_FLAGS} /WX)
+        endif()
+
+        target_compile_options(${target} PRIVATE ${WARNING_FLAGS})
     endif()
 
     # Suppress C++-specific OpenCV warning; C compiler rejects it with an error