Deprecate some travis builds, use GitHub actions instead

.travis.yml

@@ -14,18 +14,12 @@ jobs:
     include:
         - stage: "Build"
           name: "Linux Installer"
+          if: branch = master
           os: linux
           dist: bionic
           env: SPEC=linux-g++-64 CONFIG=installer
           sudo: required
         - stage: "Build"
-          name: "Linux Debug"
-          os: linux
-          dist: bionic
-          env: SPEC=linux-g++-64 CONFIG=debug
-          services: xvfb
-          sudo: required
-        - stage: "Build"
           name: "Android 32 bit"
           dist: xenial
           language: android
@@ -39,6 +33,7 @@ jobs:
           sudo: false
         - stage: "Build"
           name: "OSX Installer"
+          if: branch = master
           os: osx
           osx_image: xcode11.3
           env: SPEC=macx-clang CONFIG=installer