Reattaching libs when lib folder does not exists throws exception

As the lib folder is now per configuration there are use cases (like
imported projects) where it is expected the folder does not yet exists.
So just create the folder if it does not exists.

Author: jan

io.sloeber.core/src/io/sloeber/core/internal/SloeberConfiguration.java

@@ -586,6 +586,9 @@ public void reAttachLibraries() {
 		// Remove all existing lib folders that are not known or are linking to the
 		// wrong lib
 		try {
+			if(!libFolder.exists()) {
+				libFolder.create(true, true, new NullProgressMonitor());
+			}
 			for (IResource curResource : libFolder.members()) {
 				if (curResource instanceof IFolder) {
 					IFolder curFolder = (IFolder) curResource;