CI: build: fallback to compile toolchain if external toolchain fail

If for whatever reason external toolchain can't be found or downloaded,
fallback to internal toolchain build.

This can be useful when new target are introduced and external toolchain
are not present in openwrt fileserver.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>

.github/workflows/build.yml

@@ -189,6 +189,8 @@ jobs:
             TOOLCHAIN_SHA256=$(echo "$TOOLCHAIN_STRING" | cut -d ' ' -f 1)
 
             echo "toolchain-type=external_sdk" >> $GITHUB_OUTPUT
+          else
+            echo "toolchain-type=internal" >> $GITHUB_OUTPUT
           fi
 
           echo "TOOLCHAIN_FILE=$TOOLCHAIN_FILE" >> "$GITHUB_ENV"
@@ -196,7 +198,7 @@ jobs:
           echo "TOOLCHAIN_PATH=$TOOLCHAIN_PATH" >> "$GITHUB_ENV"
 
       - name: Cache external toolchain/sdk
-        if: inputs.build_toolchain == false
+        if: inputs.build_toolchain == false && steps.parse-toolchain.outputs.toolchain-type != 'internal'
         id: cache-external-toolchain
         uses: actions/cache@v3
         with:
@@ -212,7 +214,7 @@ jobs:
             ccache-kernel-${{ env.TARGET }}/${{ env.SUBTARGET }}-
 
       - name: Download external toolchain/sdk
-        if: inputs.build_toolchain == false && steps.cache-external-toolchain.outputs.cache-hit != 'true'
+        if: inputs.build_toolchain == false && steps.cache-external-toolchain.outputs.cache-hit != 'true' && steps.parse-toolchain.outputs.toolchain-type != 'internal'
         shell: su buildbot -c "sh -e {0}"
         working-directory: openwrt
         run: |
@@ -311,7 +313,7 @@ jobs:
             --config ${{ env.TARGET }}/${{ env.SUBTARGET }}
 
       - name: Configure internal toolchain
-        if: inputs.build_toolchain == true
+        if: inputs.build_toolchain == true || steps.parse-toolchain.outputs.toolchain-type == 'internal'
         shell: su buildbot -c "sh -e {0}"
         working-directory: openwrt
         run: |