Add Mac OS X CI.

Signed-off-by: Ricky Zhang <rickyzhang@gmail.com>

.travis.yml

@@ -30,6 +30,9 @@ matrix:
       env :
         - SDL_MAJOR_VERSION=2
         - ADDRESSING_MODE=banks
+    - os: osx
+      compiler: clang
+      osx_image: xcode12
 
 addons:
   apt:
@@ -37,12 +40,17 @@ addons:
       - libsdl1.2-dev
       - libgtk2.0-dev
       - libsdl2-dev
+  homebrew:
+    packages:
+      - sdl2
+      - autoconf
+      - make
 
 script:
   - ERR_CODE=0
+  - cd BasiliskII/src/Unix
+  - NO_CONFIGURE=1 ./autogen.sh
   - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then
-        cd BasiliskII/src/Unix;
-        NO_CONFIGURE=1 ./autogen.sh;
         if [[ $SDL_MAJOR_VERSION == *"1"* ]]; then
             ./configure --enable-sdl-video --enable-sdl-audio --disable-vosf --disable-jit-compiler --with-x --with-gtk --with-mon --enable-addressing=$ADDRESSING_MODE;
             make -j 4 || ERR_CODE=$?;
@@ -50,5 +58,8 @@ script:
             ./configure --enable-sdl-video --enable-sdl-audio --disable-vosf --disable-jit-compiler --with-x --with-gtk --with-mon --with-sdl2 --enable-addressing=$ADDRESSING_MODE;
             make -j 4 || ERR_CODE=$?;
         fi
+    else
+        ./configure --enable-sdl-video --enable-sdl-audio --disable-vosf --disable-jit-compiler --with-gtk=no --with-mon --with-sdl2 --enable-addressing=banks;
+        make -j 4 || ERR_CODE=$?;
     fi
   - (exit $ERR_CODE)