Bootstrap clingo from sources (#21446)

* Allow the bootstrapping of clingo from sources

Allow python builds with system python as external
for MacOS

* Ensure consistent configuration when bootstrapping clingo

This commit uses context managers to ensure we can
bootstrap clingo using a consistent configuration
regardless of the use case being managed.

* Github actions: test clingo with bootstrapping from sources

* Add command to inspect and clean the bootstrap store

 Prevent users to set the install tree root to the bootstrap store

* clingo: documented how to bootstrap from sources

Co-authored-by: Gregory Becker <becker33@llnl.gov>
(cherry picked from commit 10e9e142b7)

.github/workflows/linux_unit_tests.yaml

@@ -15,6 +15,7 @@ jobs:
     strategy:
       matrix:
         python-version: [2.7, 3.5, 3.6, 3.7, 3.8, 3.9]
+        concretizer: ['original', 'clingo']
 
     steps:
     - uses: actions/checkout@v2
@@ -50,16 +51,23 @@ jobs:
           mkdir -p ${KCOV_ROOT}/build
           cd ${KCOV_ROOT}/build && cmake -Wno-dev ${KCOV_ROOT}/kcov-${KCOV_VERSION} && cd -
           make -C ${KCOV_ROOT}/build && sudo  make -C ${KCOV_ROOT}/build install
+    - name: Bootstrap clingo from sources
+      if: ${{ matrix.concretizer == 'clingo' }}
+      run: |
+          . share/spack/setup-env.sh
+          spack external find --not-buildable cmake bison
+          spack -v solve zlib
     - name: Run unit tests
       env:
           COVERAGE: true
+          SPACK_TEST_SOLVER: ${{ matrix.concretizer }}
       run: |
           share/spack/qa/run-unit-tests
           coverage combine
           coverage xml
     - uses: codecov/codecov-action@v1
       with:
-        flags: unittests,linux
+        flags: unittests,linux,${{ matrix.concretizer }}
   shell:
     runs-on: ubuntu-latest
     steps:
@@ -103,6 +111,7 @@ jobs:
     - uses: codecov/codecov-action@v1
       with:
         flags: shelltests,linux
+
   centos6:
     # Test for Python2.6 run on Centos 6
     runs-on: ubuntu-latest
@@ -117,27 +126,7 @@ jobs:
           git fetch origin ${{ github.ref }}:test-branch
           git checkout test-branch
           share/spack/qa/run-unit-tests
-  clingo:
-    # Test for the clingo based solver
-    runs-on: ubuntu-latest
-    container: spack/github-actions:clingo
-    steps:
-      - name: Run unit tests
-        run: |
-          whoami && echo PWD=$PWD && echo HOME=$HOME && echo SPACK_TEST_SOLVER=$SPACK_TEST_SOLVER
-          which clingo && clingo --version
-          git clone https://github.com/spack/spack.git && cd spack
-          git fetch origin ${{ github.ref }}:test-branch
-          git checkout test-branch
-          . share/spack/setup-env.sh
-          spack compiler find
-          spack solve mpileaks%gcc
-          coverage run $(which spack) unit-test -v
-          coverage combine
-          coverage xml
-      - uses: codecov/codecov-action@v1
-        with:
-          flags: unittests,linux,clingo
+
   clingo-cffi:
     # Test for the clingo based solver (using clingo-cffi)
     runs-on: ubuntu-latest