ci: Selectively check out submodules

Check out only the needed submodules in each job to reduce unnecessary
network load and job preparation time.

This will be especially important later when host tool components, such
as QEMU, are added as submodules.

Signed-off-by: Stephanos Ioannidis <[email protected]>

Author: stephanosio

.github/workflows/ci.yml

@@ -566,17 +566,29 @@ jobs:
       if: ${{ github.event_name != 'pull_request_target' }}
       uses: actions/checkout@v4
       with:
-        submodules: recursive
         persist-credentials: false
 
     - name: Check out source code (pull request)
       if: ${{ github.event_name == 'pull_request_target' }}
       uses: actions/checkout@v4
       with:
         ref: ${{ github.event.pull_request.head.sha }}
-        submodules: recursive
         persist-credentials: false
 
+    - name: Check out submodules
+      run: |
+        git submodule init
+        git submodule update --recursive crosskit/crosskit-x86_64-apple-darwin
+        git submodule update --recursive crosskit/crosskit-x86_64-darwin-libpython
+        git submodule update --recursive crosskit/crosskit-mingw-w64-libpython
+        git submodule update --recursive crosstool-ng
+        git submodule update --recursive binutils
+        git submodule update --recursive binutils_arc
+        git submodule update --recursive gdb
+        git submodule update --recursive gcc
+        git submodule update --recursive gcc_arc
+        git submodule update --recursive picolibc
+
     - name: Build crosstool-ng
       run: |
         # Configure macOS build environment
@@ -884,17 +896,21 @@ jobs:
       if: ${{ github.event_name != 'pull_request_target' }}
       uses: actions/checkout@v4
       with:
-        submodules: recursive
         persist-credentials: false
 
     - name: Check out source code (pull request)
       if: ${{ github.event_name == 'pull_request_target' }}
       uses: actions/checkout@v4
       with:
         ref: ${{ github.event.pull_request.head.sha }}
-        submodules: recursive
         persist-credentials: false
 
+    - name: Check out submodules
+      run: |
+        git submodule init
+        git submodule update --recursive llvm
+        git submodule update --recursive picolibc
+
     - name: Setup debug session (pre)
       if: always() && needs.setup.outputs.debug == 'toolchain-pre'
       uses: mxschmitt/action-tmate@v3
@@ -1020,17 +1036,19 @@ jobs:
       if: ${{ github.event_name != 'pull_request_target' }}
       uses: actions/checkout@v4
       with:
-        submodules: recursive
         persist-credentials: false
 
     - name: Check out source code (pull request)
       if: ${{ github.event_name == 'pull_request_target' }}
       uses: actions/checkout@v4
       with:
         ref: ${{ github.event.pull_request.head.sha }}
-        submodules: recursive
         persist-credentials: false
 
+    - name: Check out submodules
+      run: |
+        git submodule init
+
     - name: Configure AWS Credentials
       uses: aws-actions/configure-aws-credentials@v4
       with: