automation: add alpine linux x86 build jobs

Allow failure for these jobs. Currently they fail because hvmloader
doesn't build with musl. The failures don't block the pipeline.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>
Acked-by: Wei Liu <wl@xen.org>

automation/gitlab-ci/build.yaml

@@ -410,6 +410,31 @@ opensuse-leap-gcc-debug:
   variables:
     CONTAINER: suse:opensuse-leap
 
+alpine-3.12-gcc:
+  extends: .gcc-x86-64-build
+  variables:
+    CONTAINER: alpine:3.12
+  allow_failure: true
+
+alpine-3.12-gcc-debug:
+  extends: .gcc-x86-64-build-debug
+  variables:
+    CONTAINER: alpine:3.12
+  allow_failure: true
+
+alpine-3.12-clang:
+  extends: .gcc-x86-64-build
+  variables:
+    CONTAINER: alpine:3.12
+  allow_failure: true
+
+alpine-3.12-clang-debug:
+  extends: .gcc-x86-64-build-debug
+  variables:
+    CONTAINER: alpine:3.12
+  allow_failure: true
+
+
 # Arm builds
 
 debian-unstable-gcc-arm64: