Move build tests from GA to Gitlab (spack#25120)

Modifications:

- Remove the "build tests" workflow from GitHub Actions
- Setup a similar e2e test on Gitlab

In this way we'll reduce load on GitHub Actions workflows and for e2e tests will
benefit from the buildcache reuse granted by pipelines.

README.md

@@ -1,7 +1,6 @@
 # <img src="https://cdn.rawgit.com/spack/spack/develop/share/spack/logo/spack-logo.svg" width="64" valign="middle" alt="Spack"/> Spack
 
 [![Unit Tests](https://github.com/spack/spack/workflows/linux%20tests/badge.svg)](https://github.com/spack/spack/actions)
-[![Linux Builds](https://github.com/spack/spack/workflows/linux%20builds/badge.svg)](https://github.com/spack/spack/actions)
 [![macOS Builds (nightly)](https://github.com/spack/spack/workflows/macOS%20builds%20nightly/badge.svg?branch=develop)](https://github.com/spack/spack/actions?query=workflow%3A%22macOS+builds+nightly%22)
 [![codecov](https://codecov.io/gh/spack/spack/branch/develop/graph/badge.svg)](https://codecov.io/gh/spack/spack)
 [![Read the Docs](https://readthedocs.org/projects/spack/badge/?version=latest)](https://spack.readthedocs.io)

share/spack/gitlab/cloud_pipelines/.gitlab-ci.yml

@@ -62,7 +62,7 @@ default:
 # TEMPLATE FOR ADDING ANOTHER PIPELINE
 ########################################
 #
-# First add a new spack.yml defining the pipline to run in
+# First add a new spack.yml defining the pipeline to run in
 # share/spack/gitlab/cloud_pipelines/stacks/my-super-cool-stack/spack.yaml
 #
 # Then add the following entries at the bottom of this file:
@@ -158,3 +158,33 @@ e4s-on-power-develop-build:
       - artifact: jobs_scratch_dir/cloud-ci-pipeline.yml
         job: e4s-on-power-develop-generate
     strategy: depend
+
+
+#########################################
+# Build tests for different build-systems
+#########################################
+.build_systems:
+  variables:
+    SPACK_CI_STACK_NAME: build_systems
+
+build_systems-pr-generate:
+  extends: [ ".build_systems", ".pr-generate"]
+
+build_systems-develop-generate:
+  extends: [ ".build_systems", ".develop-generate"]
+
+build_systems-pr-build:
+  extends: [ ".build_systems", ".pr-build" ]
+  trigger:
+    include:
+      - artifact: jobs_scratch_dir/cloud-ci-pipeline.yml
+        job: build_systems-pr-generate
+    strategy: depend
+
+build_systems-develop-build:
+  extends: [ ".build_systems", ".develop-build" ]
+  trigger:
+    include:
+      - artifact: jobs_scratch_dir/cloud-ci-pipeline.yml
+        job: build_systems-develop-generate
+    strategy: depend

share/spack/gitlab/cloud_pipelines/stacks/build_systems/spack.yaml

@@ -0,0 +1,61 @@
+spack:
+  view: false
+  concretization: separately
+
+  config:
+    install_tree:
+      root: /home/software/spack
+      padded_length: 512
+      projections:
+        all: '{architecture}/{compiler.name}-{compiler.version}/{name}-{version}-{hash}'
+
+  definitions:
+    - default_specs:
+      - lz4  # MakefilePackage
+      - mpich~fortran  # AutotoolsPackage
+      - tut  # WafPackage
+      - py-setuptools  # PythonPackage
+      - openjpeg  # CMakePackage
+      - r-rcpp  # RPackage
+      - ruby-rake  # RubyPackage
+    - arch:
+      - '%gcc@7.5.0 arch=linux-ubuntu18.04-x86_64'
+
+  specs:
+    - matrix:
+        - - $default_specs
+        - - $arch
+
+  mirrors: { "mirror": "s3://spack-binaries-develop/build_systems" }
+
+  gitlab-ci:
+    script:
+      - . "./share/spack/setup-env.sh"
+      - spack --version
+      - cd ${SPACK_CONCRETE_ENV_DIR}
+      - spack env activate --without-view .
+      - spack config add "config:install_tree:projections:${SPACK_JOB_SPEC_PKG_NAME}:'morepadding/{architecture}/{compiler.name}-{compiler.version}/{name}-{version}-{hash}'"
+      - spack -d ci rebuild
+
+    mappings:
+      - match: [ 'os=ubuntu18.04' ]
+        runner-attributes:
+          image: { "name": "ghcr.io/scottwittenburg/ecpe4s-ubuntu18.04-runner-x86_64:2020-09-01", "entrypoint": [ "" ] }
+          tags: [ "spack", "public", "large", "x86_64" ]
+
+    temporary-storage-url-prefix: "s3://spack-binaries-prs/pipeline-storage"
+    broken-specs-url: "s3://spack-binaries-develop/broken-specs"
+    service-job-attributes:
+      before_script:
+        - . "./share/spack/setup-env.sh"
+        - spack --version
+        - cd share/spack/gitlab/cloud_pipelines/stacks/build_systems
+        - spack env activate --without-view .
+      image: { "name": "ghcr.io/scottwittenburg/ecpe4s-ubuntu18.04-runner-x86_64:2020-09-01", "entrypoint": [""] }
+      tags: ["spack", "public", "medium", "x86_64"]
+
+  cdash:
+    build-group: Build tests for different build systems
+    url: https://cdash.spack.io
+    project: Spack Testing
+    site: Cloud Gitlab Infrastructure