workflows: Fix openwatcom download

Author: richardg867

.github/workflows/build.yml

@@ -15,13 +15,13 @@ jobs:
 
     steps:
       - name: Install build tools
-        run: sudo apt update && sudo apt install build-essential
+        run: sudo apt update && sudo apt install build-essential xz-utils
       - name: Download OpenWatcom
         if: steps.cache.outputs.cache-hit != 'true'
         run: |
           rm -rf /opt/watcom
           mkdir /opt/watcom
-          wget -qO- https://github.com/open-watcom/open-watcom-v2/releases/download/Current-build/ow-snapshot.tar.gz | tar -xvz -C /opt/watcom
+          wget -qO- https://github.com/open-watcom/open-watcom-v2/releases/download/Current-build/ow-snapshot.tar.xz | tar Jxvz -C /opt/watcom
           echo "/opt/watcom/binl64:/opt/watcom/binl" >> $GITHUB_PATH
       - uses: actions/checkout@v2
       - name: Build `cp437`
@@ -100,4 +100,4 @@ jobs:
             **/*.COM
             amikey/*.md
             multikey/*.md
-            viakey/*.md
+            viakey/*.md