Fix github action build issue

* Move `BuildConfig.java` from `/src/generated`to `/src/main` to accomplish the building pipeline

* Add BuildConfig.java to the .gitignore

.gitignore

@@ -69,6 +69,7 @@ language/
 languages/
 gacha-mapping.js
 data/gacha_mappings.js
+BuildConfig.java
 
 # macOS
 .DS_Store

build.gradle

@@ -122,7 +122,7 @@ jar {
     from('src/main/java') {
         include '*.xml'
     }
-    new File(projectDir, "src/generated/main/java/emu/grasscutter/BuildConfig.java").text = """
+    new File(projectDir, "src/main/java/emu/grasscutter/BuildConfig.java").text = """
     package emu.grasscutter;
     public class BuildConfig {
             public static final String VERSION = \"${version}\";