Re: BUG #19727: pg-combinebackup fails to link

I wrote:
> Ross Burton <ross(at)burtonini(dot)com> writes:
>> This is a makefile dependency bug exposed in parallel builds, and can
>> be reproduced on demand with a minimal reproducer.

> Very interesting! So the problem is that the scope of the effects of
> this:
> jsonapi_shlib.o: override CPPFLAGS += -DJSONAPI_USE_PQEXPBUFFER
> isn't terribly well-defined.

I dug in the gmake manual and verified that they document this
behavior and point out that it can produce inconsistent results.
So we need to fix it. The attached seems to do the trick, but
now I wonder where else there might be similar issues. I did
a few rounds of "make -s -j32 --shuffle" and didn't see any
other compilation failures, but that isn't a very thorough test.

regards, tom lane