Remove dependency on GNAT CE when building branch

.github/workflows/selftest.yml

@@ -9,6 +9,7 @@ on: pull_request
 jobs:
   setup-alire:
     strategy:
+      fail-fast: false
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
         target: [stable, nightly, source]

action.yml

@@ -77,13 +77,64 @@ runs:
       id: find-gnat
       run: gnat --version && echo "available=true" >> $GITHUB_OUTPUT || echo "available=false" >> $GITHUB_OUTPUT
 
-    # Setup a GNAT if necessary to build from branch.
-    # We cannot use alr-install or setup-alire, as that creates infinite recursion.
-    - name: Install GNAT
+    # Setup a GNAT if necessary to build from branch. We cannot use alr-install
+    # as that creates infinite recursion. Rather than relying on the old action
+    # that sets up CE editions, we simply fetch a stable alr capable of running
+    # `alr install`, and we use that to install the latest FSF GNAT.
+
+    # BEGIN TOOLCHAIN INSTALLATION
+
+    - name: Identify need for GNAT
       if: inputs.branch != '' && steps.find-gnat.outputs.available != 'true' && steps.cache-alr.outputs.cache-hit != 'true'
-      uses: ada-actions/toolchain@ce2020
+      id: need-GNAT
+      shell: bash
+      run: echo "need=true" >> $GITHUB_OUTPUT
+
+    - name: Install GNAT (I) Linux
+      if: steps.need-GNAT.outputs.need == 'true' && runner.os == 'Linux'
+      uses: engineerd/[email protected]
+      with:
+        name: alr
+        url: alr-2.0.0-bin-x86_64-linux.zip
+        pathInArchive: bin/alr
+    - name: Install GNAT (I) macOS
+      if: steps.need-GNAT.outputs.need == 'true' && runner.os == 'macOS'
+      uses: engineerd/[email protected]
       with:
-        distrib: community
+        name: alr
+        url: alr-2.0.0-bin-x86_64-macos.zip
+        pathInArchive: bin/alr
+    - name: Install GNAT (I) Windows
+      if: steps.need-GNAT.outputs.need == 'true' && runner.os == 'Windows'
+      uses: engineerd/[email protected]
+      with:
+        name: alr.exe
+        url: alr-2.0.0-bin-x86_64-windows.zip
+        pathInArchive: bin/alr.exe
+
+    - name: Install GNAT (II)
+      if: steps.need-GNAT.outputs.need == 'true'
+      shell: bash
+      run: |
+        alr install gnat_native gprbuild --prefix=$PWD/setup_alire_prefix
+        echo REMOVAL TARGET: $(which alr)
+        rm -f $(which alr)* && echo REMOVED stable alr used for toolchain install
+
+    - name: Install GNAT (III) - Add to path (Windows)
+      if: steps.need-GNAT.outputs.need == 'true' && runner.os == 'Windows'
+      shell: pwsh
+      run: |
+        $Target = Resolve-Path .\setup_alire_prefix\bin
+        Add-Content $env:GITHUB_PATH $Target
+        echo $Target
+
+    - name: Install GNAT (III) - Add to path (!Windows)
+      if: steps.need-GNAT.outputs.need == 'true' && runner.os != 'Windows'
+      shell: bash
+      run: |
+        readlink -f "$PWD/setup_alire_prefix/bin" >> $GITHUB_PATH
+
+    # END TOOLCHAIN INSTALLATION
 
     # To run the old setup action which is javascript
     - name: Setup Node
@@ -98,6 +149,14 @@ runs:
       shell: bash
       # on Windows, backlashes mess things for bash, and powershell chokes on toJSON output
 
+    # Remove our installed toolchain as not to interfere with other
+    # actions/workflows down the line
+    - name: Remove GNAT (IV)
+      if: steps.need-GNAT.outputs.need == 'true'
+      shell: bash
+      run: |
+        rm -rf setup_alire_prefix && echo REMOVED toolchain used to build alr
+
     # Display result for the record
     - shell: bash
       run: |