Add support for Windows (#492)

This adds support for Windows.
The in-language path separator is still `/`, to ensure Pkl programs are cross-platform.

Log lines are written using CRLF endings on Windows.
Modules that are combined with `--module-output-separator` uses LF endings to ensure
consistent rendering across platforms.

`jpkl` does not work on Windows as a direct executable.
However, it can work with `java -jar jpkl`.

Additional details:

* Adjust git settings for Windows
* Add native executable for pkl cli
* Add jdk17 windows Gradle check in CI
* Adjust CI test reports to be staged within Gradle rather than by shell script.
* Fix: encode more characters that are not safe Windows paths
* Skip running tests involving symbolic links on Windows (these require administrator privileges to run).
* Introduce custom implementation of `IoUtils.relativize`
* Allow Gradle to initialize ExecutableJar `Property` values
* Add Gradle flag to enable remote JVM debugging

Co-authored-by: Philip K.F. Hölzenspies <holzensp@gmail.com>

pkl-executor/src/main/java/org/pkl/executor/EmbeddedExecutor.java

@@ -157,7 +157,15 @@ final class EmbeddedExecutor implements Executor {
 
   private static Path toDisplayPath(Path modulePath, ExecutorOptions options) {
     var rootDir = options.getRootDir();
-    return rootDir == null ? modulePath : rootDir.relativize(modulePath);
+    return rootDir == null ? modulePath : relativize(modulePath, rootDir);
+  }
+
+  // On Windows, `Path.relativize` will fail if the two paths have different roots.
+  private static Path relativize(Path path, Path base) {
+    if (path.isAbsolute() && base.isAbsolute() && !path.getRoot().equals(base.getRoot())) {
+      return path;
+    }
+    return base.relativize(path);
   }
 
   @Override

pkl-executor/src/test/kotlin/org/pkl/executor/EmbeddedExecutorTest.kt

@@ -15,6 +15,7 @@ import org.pkl.commons.test.FilteringClassLoader
 import org.pkl.commons.test.PackageServer
 import org.pkl.commons.toPath
 import org.pkl.core.Release
+import java.io.File
 import java.nio.file.Files
 import java.nio.file.Path
 import java.time.Duration
@@ -197,9 +198,10 @@ class EmbeddedExecutorTest {
         Executors.embedded(listOf("/non/existing".toPath()))
     }
 
+    val sep = File.separatorChar
     assertThat(e.message)
       .contains("Cannot find Jar file")
-      .contains("/non/existing")
+      .contains("${sep}non${sep}existing")
   }
 
   @Test