Add note for why we are throwing on a missing file, for potential forks

build.gradle

@@ -181,6 +181,9 @@ static def nextFeatherVersion(ENV, version_id) {
 				}
 			}
 		} catch (FileNotFoundException e) {
+			// Note: we consider it a hard failure if the maven-metadata.xml file does
+			// not exist. However if you don't have this file yet, you can comment out
+			// the line below to start at build number 1.
 			throw new RuntimeException(e);
 		}