makepkg: add check to ensure we have non-URL files in build dir

Pacman 3.0 printed the following message if a file could not be found:
  ERROR: xxx was not found in the build directory and is not a proper URL.

We lost this logic in 3.1 when moving to the DLAGENT type stuff, so a
not-found file got passed all the way to the download logic where it failed
with a odd error message. Bring back some logic to ensure only files with
URLs get past a certain point, and fail if the file is not available.

Fixes FS#9208.

Signed-off-by: Dan McGee <dan@archlinux.org>

scripts/makepkg.sh.in

@@ -464,6 +464,12 @@ download_sources() {
 			continue
 		fi
 
+		# if we get here, check to make sure it was a URL, else fail
+		if [ "$file" = "$netfile" ]; then
+			error "$(gettext "%s was not found in the build directory and is not a URL.")" "$netfile"
+			exit 1 # $E_MISSING_FILE
+		fi
+
 		# find the client we should use for this URL
 		local dlclient=$(get_downloadclient $netfile) || exit $?