build: make generateApi optional when compiling project

Initially generated module was not included to the project VCS.
Since it's now in the separate src folder, we don't need to call generator every time.
Only when a new generation result is required.

imgui-binding/build.gradle

@@ -24,7 +24,8 @@ test {
 }
 
 compileJava {
-    if (!System.getProperty('build.debug.generate.api.disable')) {
+    // By default we do not generate API, since we believe this should be done on purpose.
+    if (System.getProperty('build.debug.generate.api.enable')) {
         dependsOn 'generateApi'
     }
 }