implement () -> () as Runnable downcalls and upcalls

.github/workflows/pull_request.yml

@@ -57,10 +57,7 @@ jobs:
             ${{ runner.os }}-swiftpm-
       # run the actual build
       - name: Gradle build
-        run: |
-          ./gradlew build -x test --no-daemon # skip tests
-          find .
-          ./gradlew build --info --no-daemon
+        run: ./gradlew build --info --no-daemon
 
   test-swift:
     name: Swift tests (swift:${{ matrix.swift_version }} jdk:${{matrix.jdk_vendor}} os:${{ matrix.os_version }})

.gitignore

@@ -32,4 +32,4 @@ Package.resolved
 .gradletasknamecache
 
 # Ignore files generated by jextract, we always can re-generate them
-*/**/*.java
+*/**/src/generated/java/**/*