[bug#40556] [PATCH] gnu: dovecot: Add libunwind input.

[Pierre Langlois <pierre.langlois@gmx.com>]

Pierre Langlois writes:

> Hi Ludo!
>
> Ludovic Courtès writes:
>
>> Hi,
>>
>> Pierre Langlois <pierre.langlois@gmx.com> skribis:
>>
>>> +       ;; FIXME: The 'test-backtrace' tests fail on arm when using glibc's
>>> +       ;; backtrace_symbol() function so fallback to using libunwind.
>>> +       ,@(match (or (%current-target-system) (%current-system))
>>> +           ((or "aarch64-linux" "armhf-linux")
>>> +            `(("libunwind" ,libunwind)))
>>> +           (_ '()))
>>
>> This isn’t quite correct because ‘%current-target-system’ returns a
>> triplet, like “arm-linux-gnueabihf”.
>
> Oups, I didn't realize the cross-compilation target was different.
>
>>
>> Use ‘target-arm?’ instead.
>
> Yep, that works really nicely, it's much clearer.
>
> I've tested on x86_64, arm and aarch64 natively. I'll try
> cross-compiling with --target=arm-linux-gnueabihf and
> --target=aarch64-linux-gnu as well but that'll take a little longer.

Right, it seems dovecot isn't yet cross-compilable, but cross-compiling
libunwind works just fine. With dovecot I get a failure trying to
compile perl natively, as openssl's native-input I believe.

```
$ ./pre-inst-env guix build --target=aarch64-linux-gnu openssl
...
phase `install' succeeded after 21.6 seconds
starting phase `remove-extra-references'
Backtrace:
          14 (primitive-load "/gnu/store/p51mz7mawiixjly3579bfyfv4hx…")
In ice-9/eval.scm:
   191:35 13 (_ _)
In ice-9/boot-9.scm:
    829:9 12 (catch _ _ #<procedure 7ffff3bba518 at /gnu/store/w3jl…> …)
In srfi/srfi-1.scm:
   863:16 11 (every1 #<procedure 7ffff2d50cc0 at /gnu/store/w3jlc8p…> …)
In /gnu/store/w3jlc8pk8416m7h677r5vq92b66h8cqd-module-import/guix/build/gnu-build-system.scm:
   839:30 10 (_ _)
In ice-9/eval.scm:
    619:8  9 (_ #(#(#(#(#(#(#<directory (guile-user)…>) …) …) …) …) …))
In ice-9/boot-9.scm:
    841:4  8 (with-throw-handler _ _ _)
In ice-9/ports.scm:
   445:17  7 (call-with-input-file _ _ #:binary _ #:encoding _ # _)
In /gnu/store/w3jlc8pk8416m7h677r5vq92b66h8cqd-module-import/guix/build/utils.scm:
   739:26  6 (_ _)
   765:26  5 (_ #<input: /gnu/store/kbsn60lnf6vyim3b511qvnadlldmjv1…> …)
In srfi/srfi-1.scm:
   466:18  4 (fold #<procedure 7ffff3b98790 at /gnu/store/w3jlc8pk8…> …)
In ice-9/eval.scm:
   202:51  3 (_ #(#(#(#(#(#(#<directory (guile-user)…> …)) …) …) …) …))
    163:9  2 (_ #(#(#(#(#(#(#<directory (guile-user)…> …)) …) …) …) …))
In unknown file:
           1 (string-append "incpth='" #f "/include'\n")
In ice-9/boot-9.scm:
   752:25  0 (dispatch-exception _ _ _)

ice-9/boot-9.scm:752:25: In procedure dispatch-exception:
In procedure string-append: Wrong type (expecting string): #f
builder for `/gnu/store/50wrwqkvryprlghiqnx3aq8w7ss8mak6-perl-5.30.0.drv' failed with exit code 1
build of /gnu/store/50wrwqkvryprlghiqnx3aq8w7ss8mak6-perl-5.30.0.drv failed
View build log at '/var/log/guix/drvs/50/wrwqkvryprlghiqnx3aq8w7ss8mak6-perl-5.30.0.drv.bz2'.
guix build: error: build of `/gnu/store/50wrwqkvryprlghiqnx3aq8w7ss8mak6-perl-5.30.0.drv' failed
```

But, I think perl has been fixed on core-updates, so we should be good
for this!

Thanks,
Pierre