Add Ubuntu 20.04 to GH Action build job

Author: gsingh93

.github/actions/build-kernel/action.yml

@@ -36,11 +36,20 @@ runs:
           libssl-dev \
           ncurses-dev \
           llvm \
-          clang \
           clang-tools \
           lld \
           lz4 \
-          pahole
+          xz-utils
+
+    - name: Install pahole
+      if: ${{ inputs.os == 'ubuntu-22.04' }}
+      shell: bash
+      run: sudo apt install pahole
+
+    - name: Install pahole
+      if: ${{ inputs.os == 'ubuntu-20.04' }}
+      shell: bash
+      run: sudo apt install dwarves
 
     - name: Install x86_64 dependencies
       if: ${{ inputs.arch == 'x86_64' }}

.github/workflows/build.yml

@@ -6,8 +6,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        # TODO: Add 20.04
-        os: [ubuntu-22.04]
+        os: [ubuntu-22.04, ubuntu-20.04]
         kernel: [{ack: 0, version: 5.10.y}, {ack: 0, version: 5.15.y}, {ack: 0, version: 6.1.y}, {ack: 1, version: android13-5.10-lts}]
         arch: [arm64, x86_64]
     runs-on: ${{ matrix.os }}
@@ -70,7 +69,7 @@ jobs:
       id: cache-kernel
       uses: actions/cache@v3
       with:
-        key: ${{ env.VERSION }}-${{ matrix.arch }}
+        key: ${{ matrix.os }}-${{ env.VERSION }}-${{ matrix.arch }}
         path: |
           ${{ steps.vars.outputs.KERNEL_IMAGE }}
           ${{ steps.vars.outputs.OUT_DIR }}/vmlinux
@@ -96,12 +95,14 @@ jobs:
         echo "SUFFIX=$SUFFIX" >> $GITHUB_ENV
 
     - name: Upload kernel image artifact
+      if: ${{ matrix.os == 'ubuntu-22.04' }}
       uses: actions/upload-artifact@v3
       with:
         name: kernel-image
         path: ${{ steps.vars.outputs.KERNEL_IMAGE }}-${{ env.SUFFIX }}
 
     - name: Upload vmlinux artifact
+      if: ${{ matrix.os == 'ubuntu-22.04' }}
       uses: actions/upload-artifact@v3
       with:
         name: vmlinux

Makefile

@@ -157,7 +157,7 @@ $(CLANG_DIR):
 	tar -xf clang.tar.xz -C $(CLANG_DIR) --strip-components=1
 
 .PHONY: linux_defconfig
-linux_defconfig $(LINUX_CONFIG): $(LINUX_CONFIG_FRAGMENT)
+linux_defconfig $(LINUX_CONFIG): $(LINUX_CONFIG_FRAGMENT) | $(CLANG_DIR)
 	+ $(LINUX_MAKE) $(LINUX_DEFCONFIG)
 	KCONFIG_CONFIG=$(LINUX_CONFIG) \
 		$(LINUX_SRC)/scripts/kconfig/merge_config.sh \