attempt to add vulkan linux deps for travis

.travis.yml

@@ -49,6 +49,7 @@ jobs:
             - libfuse2:i386
             - zlib1g:i386
             - unzip
+            - libvulkan-dev:i386
       before_script:
         - export ARCH=i686
         - sh scripts/travis_common_deps.sh
@@ -137,6 +138,7 @@ jobs:
             - libstdc++6
             - libfuse2
             - unzip
+            - libvulkan-dev
       before_script:
         - export ARCH=x86_64
         - sh scripts/travis_common_deps.sh

scripts/travis_linux_deps.sh

@@ -2,3 +2,9 @@
 curl http://libsdl.org/release/SDL2-$SDL_VERSION.zip -o SDL2.zip
 unzip -q SDL2.zip
 mv SDL2-$SDL_VERSION SDL2_src
+
+# ref_vk required Vulkan SDK
+wget -qO - https://packages.lunarg.com/lunarg-signing-key-pub.asc | sudo apt-key add -
+sudo wget -qO /etc/apt/sources.list.d/lunarg-vulkan-focal.list https://packages.lunarg.com/vulkan/lunarg-vulkan-focal.list
+sudo apt update
+sudo apt install vulkan-sdk