package/ci: fix and speed up the Emscripten build.

package/ci/travis.yml

@@ -110,12 +110,14 @@ matrix:
     - TARGET_GLES2=OFF
   - language: cpp
     os: osx
+    osx_image: xcode9.3
     env:
     - JOBID=emscripten-webgl1
     - TARGET=emscripten
     - TARGET_GLES2=ON
   - language: cpp
     os: osx
+    osx_image: xcode9.3
     env:
     - JOBID=emscripten-webgl2
     - TARGET=emscripten
@@ -188,7 +190,7 @@ install:
 - if [ "$TRAVIS_OS_NAME" == "osx" ] && [[ "$CMAKE_CXX_FLAGS" == *"--coverage"* ]]; then HOMEBREW_NO_AUTO_UPDATE=1 brew install lcov; fi
 - if [ "$TRAVIS_OS_NAME" == "osx" ] && [ "$TARGET" == "desktop" ]; then export PLATFORM_GL_API=CGL; fi
 - if [ "$TRAVIS_OS_NAME" == "osx" ] && [ "$TARGET" == "ios-simulator" ]; then gem install xcpretty; fi
-- if [ "$TRAVIS_OS_NAME" == "osx" ] && [ "$TARGET" == "emscripten" ]; then brew install emscripten && export LLVM=/usr/local/opt/emscripten/libexec/llvm/bin && emcc; fi
+- if [ "$TRAVIS_OS_NAME" == "osx" ] && [ "$TARGET" == "emscripten" ]; then HOMEBREW_NO_AUTO_UPDATE=1 brew install emscripten && export LLVM=/usr/local/opt/emscripten/libexec/llvm/bin && emcc; fi
 - if [ "$TARGET" == "desktop" ] || [ "$TARGET" == "desktop-sanitizers" ] || [ "$TARGET" == "desktop-gles" ]; then printf "[General]\ndrivers=null" > ~/.alsoftrc; fi
 
 # SDL on macOS and iOS (cached)