Add CI configuration for wiiu

== DETAILS

Mirroring the Wii config, I've added a config for the Wii U.

== TESTING

I pushed to a branch on the Gitlab server and verified the CI runs
successfully.

.gitlab-ci.yml

@@ -86,7 +86,7 @@ build-static-retroarch-libnx-aarch64:
     - "mkdir .retroarch-precompiled"
     - "cp -r ./* .retroarch-precompiled/"
     - "mv .retroarch-precompiled/ retroarch-precompiled/"
-    
+
 build-static-retroarch-dummy-libnx-aarch64:
   image: $CI_SERVER_HOST:5050/libretro-infrastructure/libretro-build-libnx-devkitpro:latest
   stage: build
@@ -141,7 +141,7 @@ build-static-retroarch-dummy-vita:
   dependencies: []
   script:
     - "make -f Makefile.vita.salamander -j$NUMPROC"
-  
+
 build-static-retroarch-ps2:
   image: $CI_SERVER_HOST:5050/libretro-infrastructure/libretro-build-ps2:latest
   stage: prepare-for-static-cores
@@ -247,6 +247,39 @@ build-static-retroarch-dummy-ctr:
     - "cp -f libretro-common/audio/dsp_filters/*.dsp ${MEDIA_PATH}/${CI_PROJECT_NAME}/filters/audio"
     - "cp -f gfx/video_filters/*.filt ${MEDIA_PATH}/${CI_PROJECT_NAME}/filters/video"
 
+build-static-retroarch-wiiu:
+  image: $CI_SERVER_HOST:5050/libretro-infrastructure/libretro-build-devkitpro:latest
+  stage: prepare-for-static-cores
+  before_script:
+    - export NUMPROC=$(($(nproc)/3))
+  artifacts:
+    paths:
+    -  retroarch-precompiled/
+    expire_in: 1 day
+  dependencies: []
+  needs:
+    # Dummy build requires no core
+    - build-static-retroarch-dummy-wiiu
+  script:
+    # Allow failure since we don't have a core
+    - "make -f Makefile.wiiu -j$NUMPROC ||:"
+    - "mkdir .retroarch-precompiled"
+    - "cp -r ./* .retroarch-precompiled/"
+    - "mv .retroarch-precompiled/ retroarch-precompiled/"
+
+build-static-retroarch-dummy-wiiu:
+  image: $CI_SERVER_HOST:5050/libretro-infrastructure/libretro-build-devkitpro:latest
+  stage: build
+  before_script:
+    - export NUMPROC=$(($(nproc)/3))
+  artifacts:
+    paths:
+    -  retroarch_wiiu_salamander.rpx
+    expire_in: 1 month
+  dependencies: []
+  script:
+    - "make -f Makefile.wiiu -j$NUMPROC SALAMANDER_BUILD=1"
+
 build-static-retroarch-wii:
   image: $CI_SERVER_HOST:5050/libretro-infrastructure/libretro-build-devkitpro:latest
   stage: prepare-for-static-cores