bug#62791: BUILT_SOURCES not honoured in parallel build?

Patch attached. Looks just fine. Thanks Reuben. I installed it. Closing ... --all the best, karl.

bug#67539: GNU Automake 1.16.5 FAILS one test objc-megademo

partially related to how Automake is calling libtool from the build rules (it is missing the --tag option), I added the tags to automake as previously posted here. (https://debbugs.gnu.org/cgi/bugreport.cgi?bug=67539) no tag defined for Objective C[1] (presumably it would be