Gradle build for Android in Unity fails, saying that it could not find intellij-core.jar

Here's what worked for me, as reported here:

1. Go into the Player Settings
2. Under Publishing Settings tick the box for Custom Gradle Template (Unity then creates a build.gradle template for you)
3. The template is in Assets > Plugins > Android > mainTemplate.gradle
4. Open that file in something like Notepad

5. Change ONLY THIS:

   repositories { jcenter() google() } to repositories { google() jcenter() }

6. Save the file then try the build again. Not a perfect solution but it should work until Unity/Android fixes the issue. I'm not sure whether this can become undone by upgrading Unity, but I do know that it has to be done per project.

Here's the only solution that worked for me since I'm behind a proxy.

1. Go to the .gradle folder (default is under C:\Users\<name>\).
2. Create a file called gradle.properties under this folder.
3. Add the following:

---

#http proxy setup
systemProp.http.proxyHost=<your proxy URL>
systemProp.http.proxyPort=<your proxy Port>
systemProp.http.nonProxyHosts=*.nonproxyrepos.com|localhost

#https proxy setup
systemProp.https.proxyHost=<your proxy URL>
systemProp.https.proxyPort=<your proxy Port>
systemProp.https.nonProxyHosts=*.nonproxyrepos.com|localhost

4. Reopen unity and build !