lightningd/test/Makefile: add missing dependency on header_versions_gen.h

[whitslack]

lightningd/test/run-find_my_abspath.c includes ../lightningd.c, which includes header_versions_gen.h, a generated header file.

lightningd/Makefile correctly declares that lightningd/lightningd.o depends on header_versions_gen.h, but lightningd/test/Makefile lacks any such declaration regarding lightningd/test/run-find_my_abspath.c, which leads to build failure:

In file included from lightningd/test/run-find_my_abspath.c:5:
lightningd/test/../lightningd.c:64:10: fatal error: header_versions_gen.h: No such file or directory
   64 | #include <header_versions_gen.h>
      |          ^~~~~~~~~~~~~~~~~~~~~~~

Declare the missing dependency in lightningd/test/Makefile so that Make will ensure that header_versions_gen.h is generated before it attempts to build lightningd/test/run-find_my_abspath.o.

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[vincenzopalazzo]

Wondering when this build error is hit in your setup?

[whitslack]

Wondering when this build error is hit in your setup?

What do you mean? It's hit during build. make -jN, where N is some number greater than 1. You have to tell Make the dependencies of each and every target that it can build, or it might try to build a target without first building that target's dependencies.

[vincenzopalazzo]

ACK 8165f99

What do you mean?

I just asked because I compile core lightning with no problem and I was wondering what was the way to reproduce it. Thanks for clarify it!

[whitslack]

I just asked because I compile core lightning with no problem and I was wondering what was the way to reproduce it.

@vincenzopalazzo: It's a probabilistic failure, apparently with a very low probability of occurring. I have done hundreds of full builds of CLN, with both hot and cold ccaches, and have never run into this particular failure before. Such is the nature of race conditions, though: if an ordering can occur, then it will occur eventually. Best to specify correct deps in the Makefile so that it never occurs. Thanks for merging.