Overhaul travis.yml in an attempt to speed up macos builds (#6988)

.travis.yml

@@ -1,9 +1,28 @@
 language: cpp
 dist: bionic
+addons:
+  apt:
+    sources:
+    - ubuntu-toolchain-r-test
+    packages:
+    - gcc-10
+    - g++-10
+    - libsdl2-dev
+    - libsdl2-ttf-dev
+    - libasound2-dev
+    - libxinerama-dev
+    - libxi-dev
+    - qt5-default
+    update: true
+  homebrew:
+    packages:
+    - sdl2
+    - sdl2_ttf
+    update: true
 jobs:
   include:
     - os: osx
-      osx_image: xcode11.5
+      osx_image: xcode11.6
       compiler: clang
       env: SUBTARGET=tiny   MAME=mametiny64
     - os: linux
@@ -27,13 +46,6 @@ script:
     elif [ $TRAVIS_OS_NAME == 'osx' ]; then
     unset LDOPTS && make -j2 OPTIMIZE=0 USE_LIBSDL=1 TOOLS=1 && ./$MAME -validate;
     fi
-sudo: required
-before_install:
-  - "if [ ${TRAVIS_OS_NAME:-'linux'} = 'linux' ]; then sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y; fi"
-  - "if [ ${TRAVIS_OS_NAME:-'linux'} = 'linux' ]; then sudo apt-get update -qq; fi"
-  - "if [ ${TRAVIS_OS_NAME:-'linux'} = 'linux' ]; then sudo apt-get install -y --force-yes gcc-10 g++-10 libsdl2-dev libsdl2-ttf-dev libasound2-dev libxinerama-dev libxi-dev qt5-default; fi"
-  - "if [ ${TRAVIS_OS_NAME:-'linux'} = 'osx' ]; then brew update; fi"
-  - "if [ ${TRAVIS_OS_NAME:-'linux'} = 'osx' ]; then brew install sdl2 sdl2_ttf; fi"
 branches:
   only:
     - master