Update bashbrew to fail more directly on missing library files

This works around the busybox "readlink" implementation being slightly different from GNU's which would cause failures without any error output.

bashbrew.sh

@@ -186,6 +186,12 @@ for repoTag in "${repos[@]}"; do
 			repoFile="$library/$repo"
 		fi
 		
+		if [ ! -f "$repoFile" ]; then
+			echo >&2 "error: '$repoFile' does not exist!"
+			didFail=1
+			continue
+		fi
+		
 		repoFile="$(readlink -f "$repoFile")"
 		echo "$repoTag ($repoFile)" >> "$logDir/repos.txt"