fix(windows): Escape back-slashes for gradle config jdk path (#1876)

Author: breautek

lib/builders/ProjectBuilder.js

@@ -319,7 +319,9 @@ class ProjectBuilder {
                  */
                 const javaHome = process.env.CORDOVA_JAVA_HOME || process.env.JAVA_HOME || false;
                 if (javaHome) {
-                    configProperties.set('java.home', javaHome);
+                    // Double escape back-slashes so that it is written as escaped back-slashes
+                    // in the gradle config. Primary an issue in window environments.
+                    configProperties.set('java.home', javaHome.replace(/\\/g, '\\\\'));
                 } else {
                     configProperties.unset('java.home');
                 }