Why `make` could hang

[uladzimir . bely]

Few days ago there was a strange hang in make caught, when it didn't finish 
with error after (probably) some broken pipe.

I've opened a bug regarding it (https://savannah.gnu.org/bugs/?61241), but was 
unable to reproduce it anymore.

What I could add here is that was inside build of ISAR, and here is a piece of 
process tree:

- u-boot-de0-nano(20272) - run.dpkg_runbui(21291) - sudo(21303) - 
build.sh(21332) - dpkg-buildpacka(21353) - rules(8481) - dh(8485) - 
rules(9106) - make(13435) - make(20188) - make(20421)

There is a piece of "walking" through the code in gdb attached to the bug.

We haven't stop the process yet, so the hanging `make` process 20421 is still 
running on the server. So, we could attach again with gdb to it and extract 
any useful information that could help to understand what had happened.

Build log is also attached to the bug and it looks like there was some broken 
pipe - but we couldn't understand why `make` didn't produce the error and 
still running at some endless loop.

-- 
Uladzimir Bely
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