Move build tests from GA to Gitlab (#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.

.github/workflows/linux_build_tests.yaml

@@ -1,77 +0,0 @@
-name: linux builds
-
-on:
-  push:
-    branches:
-    - develop
-    - releases/**
-    paths-ignore:
-      # Don't run if we only modified packages in the built-in repository
-      - 'var/spack/repos/builtin/**'
-      - '!var/spack/repos/builtin/packages/lz4/**'
-      - '!var/spack/repos/builtin/packages/mpich/**'
-      - '!var/spack/repos/builtin/packages/tut/**'
-      - '!var/spack/repos/builtin/packages/py-setuptools/**'
-      - '!var/spack/repos/builtin/packages/openjpeg/**'
-      - '!var/spack/repos/builtin/packages/r-rcpp/**'
-      - '!var/spack/repos/builtin/packages/ruby-rake/**'
-      # Don't run if we only modified documentation
-      - 'lib/spack/docs/**'
-  pull_request:
-    branches:
-    - develop
-    - releases/**
-    paths-ignore:
-      # Don't run if we only modified packages in the built-in repository
-      - 'var/spack/repos/builtin/**'
-      - '!var/spack/repos/builtin/packages/lz4/**'
-      - '!var/spack/repos/builtin/packages/mpich/**'
-      - '!var/spack/repos/builtin/packages/tut/**'
-      - '!var/spack/repos/builtin/packages/py-setuptools/**'
-      - '!var/spack/repos/builtin/packages/openjpeg/**'
-      - '!var/spack/repos/builtin/packages/r-rcpp/**'
-      - '!var/spack/repos/builtin/packages/ruby-rake/**'
-      # Don't run if we only modified documentation
-      - 'lib/spack/docs/**'
-
-jobs:
-  build:
-    runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        package:
-        - lz4  # MakefilePackage
-        - mpich~fortran  # AutotoolsPackage
-        - 'tut%gcc@:10.99.99'  # WafPackage
-        - py-setuptools  # PythonPackage
-        - openjpeg  # CMakePackage
-        - r-rcpp  # RPackage
-        - ruby-rake  # RubyPackage
-    steps:
-    - uses: actions/checkout@v2
-    - uses: actions/cache@v2.1.6
-      with:
-        path: ~/.ccache
-        key: ccache-build-${{ matrix.package }}
-        restore-keys: |
-          ccache-build-${{ matrix.package }}
-    - uses: actions/setup-python@v2
-      with:
-        python-version: 3.9
-    - name: Install System Packages
-      run: |
-        sudo apt-get update
-        sudo apt-get -yqq install ccache gfortran perl perl-base r-base r-base-core r-base-dev ruby findutils openssl libssl-dev libpciaccess-dev
-        R --version
-        perl --version
-        ruby --version
-    - name: Copy Configuration
-      run: |
-        ccache -M 300M && ccache -z
-        # Set up external deps for build tests, b/c they take too long to compile
-        cp share/spack/qa/configuration/*.yaml etc/spack/
-    - name: Run the build test
-      run: |
-        . share/spack/setup-env.sh
-        SPEC=${{ matrix.package }} share/spack/qa/run-build-tests
-        ccache -s