Testing on minimalist alpine (linux) images (#1200)

* Tweaking header includes to make it safer.

* Adding the actual tests.

* Fixing my syntax.

.github/workflows/alpine.yml

@@ -0,0 +1,27 @@
+name: Alpine Linux
+'on':
+  - push
+  - pull_request
+jobs:
+  ubuntu-build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: start docker
+        run: |
+          docker run -w /src -dit --name alpine -v $PWD:/src alpine:latest
+          echo 'docker exec alpine "$@";' > ./alpine.sh
+          chmod +x ./alpine.sh
+      - name: install packages
+        run: |
+          ./alpine.sh apk update
+          ./alpine.sh apk add build-base cmake g++ linux-headers git bash
+      - name: cmake
+        run: |
+          ./alpine.sh cmake -B build_for_alpine
+      - name: build
+        run: |
+          ./alpine.sh cmake --build build_for_alpine
+      - name: test
+        run: |
+          ./alpine.sh bash -c "cd build_for_alpine && ctest"

benchmark/linux/linux-perf-events.h

@@ -1,8 +1,16 @@
 // https://github.com/WojciechMula/toys/blob/master/000helpers/linux-perf-events.h
 #pragma once
 #ifdef __linux__
-
+#ifdef __has_include
+#if __has_include(<asm/unistd.h>)
 #include <asm/unistd.h>       // for __NR_perf_event_open
+#else
+#warning "Header asm/unistd.h cannot be found though it is a linux system. Are linux headers missing?"
+#endif
+#else // no __has_include
+// Please insure that linux headers have been installed.
+#include <asm/unistd.h>       // for __NR_perf_event_open
+#endif 
 #include <linux/perf_event.h> // for perf event constants
 #include <sys/ioctl.h>        // for ioctl
 #include <unistd.h>           // for syscall