GHA: Use matrix to de-duplicate workflow definition

The general skeleton of each job is the same, so consolidate the
definition to a single job with an explicit matrix.

Use conditional steps to handle steps that are unique to a certain job
(e.g., installing clang-11 for better ASAN support).

.github/workflows/linux.yml

@@ -2,17 +2,26 @@ name: Linux CI
 on: [push, pull_request]
 
 jobs:
-  ASAN:
+  linux:
+    name: ${{ matrix.flavor }} (cc=${{ matrix.cc }})
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        include:
+          - flavor: asan
+            cc: clang-11
+          - flavor: lint
+            cc: gcc
     env:
-      CC: clang-11
+      CC: ${{ matrix.cc }}
     steps:
       - uses: actions/checkout@v2
 
       - name: Setup commom environment variables
-        run: ./.github/workflows/env.sh asan
+        run: ./.github/workflows/env.sh ${{ matrix.flavor }}
 
       - name: Setup clang repository
+        if: matrix.flavor == 'asan'
         run: |
           wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key|sudo apt-key add -
           sudo add-apt-repository 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-11 main'
@@ -23,6 +32,7 @@ jobs:
           sudo apt-get install -y autoconf automake build-essential ccache cmake cpanminus cscope gcc-multilib gdb gettext gperf language-pack-tr libtool-bin locales ninja-build pkg-config python python-pip python-setuptools python3 python3-pip python3-setuptools unzip valgrind xclip
 
       - name: Install new clang
+        if: matrix.flavor == 'asan'
         run: sudo apt-get install -y clang-11
 
       - name: Setup interpreter packages
@@ -32,51 +42,11 @@ jobs:
 
       - name: Cache dependencies
         uses: actions/cache@v2
-        env:
-          cache-name: asan-deps
         with:
           path: |
             ${{ env.CACHE_NVIM_DEPS_DIR }}
             ~/.ccache
-          key: ${{ runner.os }}-build-${{ env.cache-name }}-${{ hashFiles('cmake/*', 'third-party/**', '**/CMakeLists.txt') }}-${{ github.base_ref }}
-
-      - name: Build third-party
-        run: ./ci/before_script.sh
-
-      - name: Build and test
-        run: ./ci/script.sh
-
-      - name: Cache dependencies
-        if: ${{ success() }}
-        run: ./ci/before_cache.sh
-
-  lint:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v2
-
-      - name: Setup commom environment variables
-        run: ./.github/workflows/env.sh lint
-
-      - name: Install apt packages
-        run: |
-          sudo apt-get update
-          sudo apt-get install -y autoconf automake build-essential ccache cmake gcc-multilib gettext gperf libtool-bin locales ninja-build pkg-config python3 python3-pip python3-setuptools unzip
-
-      - name: Setup interpreter packages
-        run: |
-          ./ci/before_install.sh
-          ./ci/install.sh
-
-      - name: Cache dependencies
-        uses: actions/cache@v2
-        env:
-          cache-name: lint-deps
-        with:
-          path: |
-            ${{ env.CACHE_NVIM_DEPS_DIR }}
-            ~/.ccache
-          key: ${{ runner.os }}-build-${{ env.cache-name }}-${{ hashFiles('cmake/*', 'third-party/**', '**/CMakeLists.txt') }}-${{ github.base_ref }}
+          key: ${{ runner.os }}-${{ matrix.flavor }}-${{ matrix.cc }}-${{ hashFiles('cmake/*', 'third-party/**', '**/CMakeLists.txt') }}-${{ github.base_ref }}
 
       - name: Build third-party
         run: ./ci/before_script.sh