GitHub Actions: only build pushes into and PR against master

This should fix the odd double builds for people who create branches for
pull requests in the main repository.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

.github/workflows/android.yml

@@ -1,5 +1,11 @@
 name: Android
-on: [push, pull_request]
+on:
+  push:
+    branches:
+    - master
+  pull_request:
+    branches:
+    - master
 
 jobs:
   buildInContainer:

.github/workflows/ios.yml

@@ -1,5 +1,11 @@
 name: iOS
-on: [push, pull_request]
+on:
+  push:
+    branches:
+    - master
+  pull_request:
+    branches:
+    - master
 
 jobs:
   mobileBuild:

.github/workflows/linux-bionic-5.9.yml

@@ -1,5 +1,11 @@
 name: Linux Qt 5.9
-on: [push, pull_request]
+on:
+  push:
+    branches:
+    - master
+  pull_request:
+    branches:
+    - master
 
 jobs:
   buildOnBionic:

.github/workflows/linux-trusty-5.12.yml

@@ -1,5 +1,11 @@
 name: Linux Qt 5.12
-on: [push, pull_request]
+on:
+  push:
+    branches:
+    - master
+  pull_request:
+    branches:
+    - master
 
 jobs:
   buildInContainer:

.github/workflows/mac.yml

@@ -1,5 +1,11 @@
 name: Mac
-on: [push, pull_request]
+on:
+  push:
+    branches:
+    - master
+  pull_request:
+    branches:
+    - master
 
 jobs:
   desktopBuild:

.github/workflows/windows.yml

@@ -1,5 +1,11 @@
 name: Windows
-on: [push, pull_request]
+on:
+  push:
+    branches:
+    - master
+  pull_request:
+    branches:
+    - master
 
 jobs:
   buildInContainer: