[perl #37323] [TODO] build - makefile dependencies

# New Ticket Created by Joshua Hoblitt
# Please include the string: [perl #37323]
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# <URL: https://rt.perl.org/rt3/Ticket/Display.html?id=37323 >

All build targets need to have properly declared dependencies. With the
current state of things, 'make' often doesn't do the right thing when
source files are edited. Nor are parallel builds (make -jN) possible.

-J

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