100% banish submodules (use package manager)

Helps hexops/mach#902

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

.github/workflows/ci.yml

@@ -23,8 +23,6 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v2
-        with:
-          submodules: 'recursive'
       - name: Setup Zig
         run: |
           sudo apt install xz-utils
@@ -54,8 +52,6 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v2
-        with:
-          submodules: 'recursive'
       - name: Setup Zig
         run: |
           $ProgressPreference = 'SilentlyContinue'
@@ -73,8 +69,6 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v2
-        with:
-          submodules: 'recursive'
       - name: Setup Zig
         run: |
           brew uninstall --ignore-dependencies libx11 # https://github.com/ziglang/zig/issues/11066