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/pkl-executor.gradle.kts

@@ -1,4 +1,5 @@
 import java.nio.file.Files
+import java.nio.file.LinkOption
 
 plugins {
   pklAllProjects
@@ -62,12 +63,23 @@ val prepareHistoricalDistributions by tasks.registering {
     val distributionDir = outputDir.get().asFile.toPath()
       .also(Files::createDirectories)
     for (file in pklHistoricalDistributions.files) {
-      val link = distributionDir.resolve(file.name)
-      if (!Files.isSymbolicLink(link)) {
-        if (Files.exists(link)) {
-          Files.delete(link)
+      val target = distributionDir.resolve(file.name)
+      // Create normal files on Windows, symlink on macOS/linux (need admin priveleges to create
+      // symlinks on Windows)
+      if (buildInfo.os.isWindows) {
+        if (!Files.isRegularFile(target, LinkOption.NOFOLLOW_LINKS)) {
+          if (Files.exists(target)) {
+            Files.delete(target)
+          }
+          Files.copy(file.toPath(), target)
+        }
+      } else {
+        if (!Files.isSymbolicLink(target)) {
+          if (Files.exists(target)) {
+            Files.delete(target)
+          }
+          Files.createSymbolicLink(target, file.toPath())
         }
-        Files.createSymbolicLink(link, file.toPath())
       }
     }
   }