CI: Allow building with internal toolchain

This adds an option to build with internal toolchain. This can be used
to build targets which are currently not build by the OpenWrt build bots
and which needs their own toolchain build for every build.

Building the toolchain takes about 30 minutes compared to using the
external toolchain which takes some seconds.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
(cherry picked from commit 08f5283392674fe874c7f441128319263ce0d171)

.github/workflows/build.yml

@@ -6,6 +6,8 @@ on:
       target:
         required: true
         type: string
+      build_toolchain:
+        type: boolean
       include_feeds:
         type: boolean
       build_full:
@@ -109,6 +111,7 @@ jobs:
           ./scripts/feeds install -a
 
       - name: Parse toolchain file
+        if: inputs.build_toolchain == false
         working-directory: openwrt
         run: |
           TOOLCHAIN_STRING="$(curl "https://downloads.cdn.openwrt.org/snapshots/targets/${{ env.TARGET }}/${{ env.SUBTARGET }}/sha256sums" \
@@ -120,6 +123,7 @@ jobs:
           echo "TOOLCHAIN_SHA256=$TOOLCHAIN_SHA256" >> "$GITHUB_ENV"
 
       - name: Cache external toolchain
+        if: inputs.build_toolchain == false
         id: cache-external-toolchain
         uses: actions/cache@v3
         with:
@@ -135,7 +139,7 @@ jobs:
             ccache-kernel-${{ env.TARGET }}/${{ env.SUBTARGET }}-
 
       - name: Download external toolchain
-        if: steps.cache-external-toolchain.outputs.cache-hit != 'true'
+        if: inputs.build_toolchain == false && steps.cache-external-toolchain.outputs.cache-hit != 'true'
         shell: su buildbot -c "sh -e {0}"
         working-directory: openwrt
         run: |
@@ -162,6 +166,7 @@ jobs:
           echo CONFIG_ALL=y >> .config
 
       - name: Configure external toolchain
+        if: inputs.build_toolchain == false
         shell: su buildbot -c "sh -e {0}"
         working-directory: openwrt
         run: |
@@ -174,6 +179,20 @@ jobs:
             --overwrite-config \
             --config ${{ env.TARGET }}/${{ env.SUBTARGET }}
 
+      - name: Configure internal toolchain
+        if: inputs.build_toolchain == true
+        shell: su buildbot -c "sh -e {0}"
+        working-directory: openwrt
+        run: |
+          echo CONFIG_DEVEL=y >> .config
+          echo CONFIG_AUTOREMOVE=y >> .config
+          echo CONFIG_CCACHE=y >> .config
+
+          echo "CONFIG_TARGET_${{ env.TARGET }}=y" >> .config
+          echo "CONFIG_TARGET_${{ env.TARGET }}_${{ env.SUBTARGET }}=y" >> .config
+
+          make defconfig
+
       - name: Show configuration
         shell: su buildbot -c "sh -e {0}"
         working-directory: openwrt