travis: Enable macOS builds

.travis.sh

@@ -71,6 +71,11 @@ travis_install() {
         download_extract_zip http://dl.google.com/android/repository/${NDK_VER}-linux-x86_64.zip ${NDK_VER}-linux-x86_64.zip
     fi
 
+    if [ "$PPSSPP_BUILD_TYPE" = "macOS" ]; then
+        brew update
+        brew install sdl2
+    fi
+
     # Ensure we're using ccache
     if [[ "$CXX" = "clang" && "$CC" == "clang" ]]; then
         export CXX="ccache clang" CC="ccache clang"
@@ -113,6 +118,9 @@ travis_script() {
     if [ "$PPSSPP_BUILD_TYPE" = "iOS" ]; then
         ./b.sh --ios
     fi
+    if [ "$PPSSPP_BUILD_TYPE" = "macOS" ]; then
+        ./b.sh --headless
+    fi
 }
 
 travis_after_success() {

.travis.yml

@@ -66,6 +66,11 @@ matrix:
       compiler: "gcc qt"
       env: PPSSPP_BUILD_TYPE=Linux
            QT=TRUE
+    - os: osx
+      osx_image: xcode8
+      compiler: "clang macos"
+      env: PPSSPP_BUILD_TYPE=macOS
+           CMAKE=TRUE
     - os: osx
       osx_image: xcode8
       compiler: "clang ios"