fix: configure gradle java.home (#1795)

Author: erisu

lib/builders/ProjectBuilder.js

@@ -286,14 +286,49 @@ class ProjectBuilder {
     prepEnv (opts) {
         const self = this;
         const config = this._getCordovaConfig();
+        const configPropertiesPath = path.join(self.root, 'tools', '.gradle', 'config.properties');
+
         return check_reqs.check_gradle()
             .then(function () {
                 events.emit('verbose', `Using Gradle: ${config.GRADLE_VERSION}`);
                 return self.installGradleWrapper(config.GRADLE_VERSION);
+            }).then(async function () {
+                try {
+                    // Try to create "config.properties" file if missing
+                    const fd = fs.openSync(configPropertiesPath, 'wx+', 0o600);
+                    fs.writeFileSync(fd, '', 'utf8');
+                    fs.closeSync(fd);
+                } catch {
+                    // File already existed, nothing to do.
+                }
+
+                // Loads "config.properties"for editing
+                const configProperties = createEditor(configPropertiesPath);
+                /*
+                 * File is replaced on each build. "before_build" hook scripts can inject
+                 * custom settings before this step runs. This step will still overwrite
+                 * the "java.home" setting. Ensure environment variables are properly
+                 * configured if want to use custom "java.home".
+                 *
+                 * Sets "java.home" using the "CORDOVA_JAVA_HOME" environment variable.
+                 * If unavailable, fallback to "JAVA_HOME".
+                 * If neither is set, "java.home" is removed (if previously set),
+                 * allowing Android Studio to display a warning and auto-configure
+                 * to use its internal (bundled) Java.
+                 */
+                const javaHome = process.env.CORDOVA_JAVA_HOME || process.env.JAVA_HOME || false;
+                if (javaHome) {
+                    configProperties.set('java.home', javaHome);
+                } else {
+                    configProperties.unset('java.home');
+                }
+                // Saves changes
+                configProperties.save();
             }).then(async function () {
                 await fsp.cp(path.join(self.root, 'tools', 'gradle'), path.join(self.root, 'gradle'), { recursive: true, force: true });
                 await fsp.cp(path.join(self.root, 'tools', 'gradlew'), path.join(self.root, 'gradlew'), { recursive: true, force: true });
                 await fsp.cp(path.join(self.root, 'tools', 'gradlew.bat'), path.join(self.root, 'gradlew.bat'), { recursive: true, force: true });
+                await fsp.cp(path.join(self.root, 'tools', '.gradle'), path.join(self.root, '.gradle'), { recursive: true, force: true });
             }).then(function () {
                 return self.prepBuildFiles();
             }).then(() => {