Check consistency and compilability of all GitHub workflows (#229)

Now that we have a workflow that runs only on demand, and not in every
PR or on the `main` branch, it's beneficial to have these extra checks.

BTW, I noticed this piece is useful in almost every project, and I'm
planning to release some kind of util (a GitHub action?) that would
encapsulate this logic. It's tracked in
typesafegithub/github-workflows-kt#213

Examples of using this approach in other repos:
*
https://github.com/typesafegithub/github-workflows-kt/blob/0e91c566849a5883b39021a5ecbc18d25b006c1b/.github/workflows/build.main.kts#L95
*
https://github.com/typesafegithub/github-actions-typing-catalog/blob/667df7ec3fc639d19e278fc5956a9f753b26bb90/.github/workflows/test.main.kts#L14

.github/workflows/build.main.kts

@@ -71,4 +71,46 @@ workflow(
             )
         }
     }
+
+    job(
+        id = "build_kotlin_scripts",
+        name = "Build Kotlin scripts",
+        runsOn = UbuntuLatest,
+    ) {
+        uses(action = Checkout())
+        run(
+            command = """
+            find -name *.main.kts -print0 | while read -d ${'$'}'\0' file
+            do
+                echo "Compiling ${'$'}file..."
+                kotlinc -Werror -Xallow-any-scripts-in-source-roots -Xuse-fir-lt=false "${'$'}file"
+            done
+            """.trimIndent()
+        )
+    }
+
+    job(
+        id = "workflows_consistency_check",
+        name = "Run consistency check on all GitHub workflows",
+        runsOn = UbuntuLatest,
+    ) {
+        uses(action = Checkout())
+        run(command = "cd .github/workflows")
+        run(
+            name = "Regenerate all workflow YAMLs",
+            command = """
+            find -name "*.main.kts" -print0 | while read -d ${'$'}'\0' file
+            do
+                if [ -x "${'$'}file" ]; then
+                    echo "Regenerating ${'$'}file..."
+                    (${'$'}file)
+                fi
+            done
+            """.trimIndent(),
+        )
+        run(
+            name = "Check if some file is different after regeneration",
+            command = "git diff --exit-code .",
+        )
+    }
 }

.github/workflows/build.yaml

@@ -109,3 +109,41 @@ jobs:
     - id: 'step-4'
       name: 'Build'
       run: './gradlew build --stacktrace'
+  build_kotlin_scripts:
+    name: 'Build Kotlin scripts'
+    runs-on: 'ubuntu-latest'
+    needs:
+    - 'check_yaml_consistency'
+    steps:
+    - id: 'step-0'
+      uses: 'actions/checkout@v4'
+    - id: 'step-1'
+      run: |-
+        find -name *.main.kts -print0 | while read -d $'\0' file
+        do
+            echo "Compiling $file..."
+            kotlinc -Werror -Xallow-any-scripts-in-source-roots -Xuse-fir-lt=false "$file"
+        done
+  workflows_consistency_check:
+    name: 'Run consistency check on all GitHub workflows'
+    runs-on: 'ubuntu-latest'
+    needs:
+    - 'check_yaml_consistency'
+    steps:
+    - id: 'step-0'
+      uses: 'actions/checkout@v4'
+    - id: 'step-1'
+      run: 'cd .github/workflows'
+    - id: 'step-2'
+      name: 'Regenerate all workflow YAMLs'
+      run: |-
+        find -name "*.main.kts" -print0 | while read -d $'\0' file
+        do
+            if [ -x "$file" ]; then
+                echo "Regenerating $file..."
+                ($file)
+            fi
+        done
+    - id: 'step-3'
+      name: 'Check if some file is different after regeneration'
+      run: 'git diff --exit-code .'