Add user additional CMake arugments at the end. (#814)

The additional CMake arguments added by the user in the launch
configuration UI are added at the end of the CMake command, such that
the user is able to override arguments set by the system.

cmake/org.eclipse.cdt.cmake.core/src/org/eclipse/cdt/cmake/core/internal/CommandDescriptorBuilder.java

@@ -78,8 +78,6 @@ CommandDescriptor makeCMakeCommandline(Path toolChainFile) throws CoreException
 			}
 		}
 		CommandDescriptorBuilder.appendCMakeArguments(args, cmakeProperties.getExtraArguments());
-		/* add settings for the operating system we are running under */
-		CommandDescriptorBuilder.appendCMakeOsOverrideArgs(args, overridesSelector.getOsOverrides(cmakeProperties));
 
 		/* at last, add our requirements that override extra args specified by the user... */
 		{
@@ -94,6 +92,10 @@ CommandDescriptor makeCMakeCommandline(Path toolChainFile) throws CoreException
 		if (toolChainFile != null) {
 			args.add("-DCMAKE_TOOLCHAIN_FILE=" + toolChainFile.toString()); //$NON-NLS-1$
 		}
+		/* Add settings for the operating system we are running under,
+		 * and the user additional CMake arguments set in the Launch Configuration UI.
+		 */
+		CommandDescriptorBuilder.appendCMakeOsOverrideArgs(args, overridesSelector.getOsOverrides(cmakeProperties));
 
 		return new CommandDescriptor(args, env);
 	}