Add tests for PATH suggestion output of installation script

The "template" installation script stored in this repository prints advice to the user about adding the installation to
their PATH environment variable.

This advice is adjusted according to whether a previous installation was found in the PATH and according to the path(s)
of their installation(s) so it is fairly complex. For this reason, it will be good to have a check in the
"Test install script" CI workflow to ensure the output is as expected.

Author: per1234

.github/workflows/test-install-script.yml

@@ -191,3 +191,78 @@ jobs:
         shell: bash
         run: |
           "${PWD}/bin/${{ env.TOOL_NAME }}" --version | grep "^nightly-"
+
+  path-suggestions:
+    needs: configure
+    strategy:
+      fail-fast: false
+
+      matrix:
+        os:
+          - ubuntu-latest
+          - windows-latest
+          - macos-latest
+
+    runs-on: ${{ matrix.os }}
+
+    steps:
+      - name: Set install path environment variables
+        shell: bash
+        run: |
+          # See: https://docs.github.com/en/free-pro-team@latest/actions/reference/workflow-commands-for-github-actions#setting-an-environment-variable
+          FIRST_INSTALLATION_FOLDER="first-installation-folder"
+          echo "FIRST_INSTALLATION_FOLDER=${FIRST_INSTALLATION_FOLDER}" >> "$GITHUB_ENV"
+          echo "FIRST_BINDIR=${{ runner.temp }}/${FIRST_INSTALLATION_FOLDER}" >> "$GITHUB_ENV"
+          SECOND_INSTALLATION_FOLDER="second-installation-folder"
+          echo "SECOND_INSTALLATION_FOLDER=${SECOND_INSTALLATION_FOLDER}" >> "$GITHUB_ENV"
+          echo "SECOND_BINDIR=${{ runner.temp }}/${SECOND_INSTALLATION_FOLDER}" >> "$GITHUB_ENV"
+
+      - name: Download script artifact
+        uses: actions/download-artifact@v2
+        with:
+          name: ${{ env.SCRIPT_ARTIFACT_NAME }}
+
+      - name: Make script executable
+        run: chmod u+x "${{ github.workspace }}/${{ env.SCRIPT_NAME }}"
+
+      - name: Check script output without previous installation in PATH
+        shell: sh
+        env:
+          BINDIR: ${{ env.FIRST_BINDIR }}
+        run: |
+          mkdir -p "${{ env.BINDIR }}"
+          "${{ github.workspace }}/${{ env.SCRIPT_NAME }}" | \
+            grep \
+              -F \
+              '${{ env.TOOL_NAME }} not found. You might want to add "${{ env.FIRST_BINDIR }}" to your $PATH'
+
+      - name: Add first installation to PATH
+        shell: bash
+        run: |
+          # See: https://docs.github.com/en/actions/reference/workflow-commands-for-github-actions#adding-a-system-path
+          echo "${{ env.FIRST_BINDIR }}" >> "$GITHUB_PATH"
+
+      - name: Check script output with previous installation in PATH (non-Windows)
+        if: runner.os != 'Windows'
+        shell: sh
+        env:
+          BINDIR: ${{ env.SECOND_BINDIR }}
+        run: |
+          mkdir -p "${{ env.BINDIR }}"
+          "${{ github.workspace }}/${{ env.SCRIPT_NAME }}" | \
+            grep \
+              -F \
+              '${{ env.TOOL_NAME }} was found at ${{ env.FIRST_BINDIR }}/${{ env.TOOL_NAME }}. Please prepend "${{ env.BINDIR }}" to your $PATH'
+
+      # ${{ runner.temp }} is a Windows style path on the windows runner, but the script output uses the equivalent POSIX style path.
+      # So a regex is used for the output check on Windows.
+      - name: Check script output with previous installation in PATH (Windows)
+        if: runner.os == 'Windows'
+        shell: sh
+        env:
+          BINDIR: ${{ env.SECOND_BINDIR }}
+        run: |
+          mkdir -p "${{ env.BINDIR }}"
+          "${{ github.workspace }}/${{ env.SCRIPT_NAME }}" | \
+            grep \
+              '${{ env.TOOL_NAME }} was found at .*/${{ env.FIRST_INSTALLATION_FOLDER }}/${{ env.TOOL_NAME }}\. Please prepend ".*/${{ env.SECOND_INSTALLATION_FOLDER }}" to your \$PATH'