simplify github workflows using the matrix syntax

.github/workflows/ci-alpine-linux.yml

@@ -4,12 +4,19 @@ on: [push, pull_request]
 
 jobs:
 
-  gcc-musl:
+  alpine:
+    name: Alpine Linux
     runs-on: ubuntu-latest
     container: alpine:latest
+    strategy:
+      fail-fast: false
+      matrix:
+        compiler:
+          - gcc
+    env:
+      CC: ${{ matrix.compiler }}
     steps:
-      - name: install deps
-        run: >-
+      - run: >-
           apk --no-cache add \
             build-base \
             meson \
@@ -18,14 +25,7 @@ jobs:
             linux-pam-dev \
             libcap \
             libcap-dev
-      - name: checkout
-        uses: actions/checkout@v2
+      - uses: actions/checkout@v2
       - run: meson setup builddir/
-        env:
-          CC: gcc
       - run: meson compile -C builddir
-        env:
-          CC: gcc
       - run: meson test --verbose -C builddir
-        env:
-          CC: gcc

.github/workflows/ci-ubuntu.yml

@@ -4,35 +4,21 @@ on: [push, pull_request]
 
 jobs:
 
-  gcc-glibc:
+  ubuntu:
+    name: Ubuntu
     runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        compiler:
+          - gcc
+          - clang
+    env:
+      CC: ${{ matrix.compiler }}
     steps:
     - uses: actions/checkout@v2
     - run: sudo apt-get update -q
-    - run: sudo apt-get install -q -y build-essential libpam-dev meson libcap-dev
+    - run: sudo apt-get install -q -y build-essential libpam-dev meson libcap-dev ${CC}
     - run: meson setup builddir/
-      env:
-        CC: gcc
     - run: ninja -C builddir
-      env:
-        CC: gcc
     - run: ninja test --verbose -C builddir
-      env:
-        CC: gcc
-
-
-  clang-glibc:
-    runs-on: ubuntu-latest
-    steps:
-    - uses: actions/checkout@v2
-    - run: sudo apt-get update -q
-    - run: sudo apt-get install -q -y build-essential clang libpam-dev meson libcap-dev
-    - run: meson setup builddir/
-      env:
-        CC: clang
-    - run: ninja -C builddir
-      env:
-        CC: clang
-    - run: ninja test --verbose -C builddir
-      env:
-        CC: clang