Work around bndtools/bnd#5695 by configuring jar tasks eagerly (#3354)

Eagerly configure Jar tasks to create the BundleTaskExtension prior to
the Gradle compileClasspath configuration becoming locked and
triggering it's beforeLocking callback to run. This allows the BND
extension to modify the LibraryElements attribute on that configuration
and request a variant with the "jar" value prior to Gradle
automatically modifying the attribute to request the "classes" value.
This ensures jars are present on the classpath for BND to use when
checked for exported classes to use when building the manifest. If it
only uses the classes directory for this task, it will not have access
to version information and will not write version info to the manifest
it is assembling for the current project, causing the verifyOSGi task
to fail.

Addresses issue bndtools/bnd#5695 and allows merging of #3351.

gradle/plugins/common/src/main/kotlin/junitbuild.osgi-conventions.gradle.kts

@@ -14,7 +14,7 @@ val projectDescription = objects.property<String>().convention(provider { projec
 // metadata into the jar
 tasks.withType<Jar>().matching { task: Jar ->
 	task.name == "jar" || task.name == "shadowJar"
-}.configureEach {
+}.all { // configure tasks eagerly as workaround for https://github.com/bndtools/bnd/issues/5695
 	extra["importAPIGuardian"] = importAPIGuardian
 
 	extensions.create<BundleTaskExtension>(BundleTaskExtension.NAME, this).apply {