Add missing include that triggers a build failure on PowerPC:

  ../../../../gcc-5.4.0/libsanitizer/asan/asan_linux.cc: In function ‘bool __asan::AsanInterceptsSignal(int)’:
  ../../../../gcc-5.4.0/libsanitizer/asan/asan_linux.cc:222:20: error: ‘SIGSEGV’ was not declared in this scope
     return signum == SIGSEGV && common_flags()->handle_segv;
		      ^
From <https://patchwork.ozlabs.org/patch/725596/>.

diff --git a/libsanitizer/asan/asan_linux.cc b/libsanitizer/asan/asan_linux.cc
index c504168..59087b9 100644
--- a/libsanitizer/asan/asan_linux.cc
+++ b/libsanitizer/asan/asan_linux.cc
@@ -29,6 +29,7 @@
 #include <dlfcn.h>
 #include <fcntl.h>
 #include <pthread.h>
+#include <signal.h>
 #include <stdio.h>
 #include <unistd.h>
 #include <unwind.h>
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<div class='path'>path: <a href='/guix/log/?id=690a347bdbb3912040a996c64851396f5922e4e7'>root</a>/<a href='/guix/log/gnu?id=690a347bdbb3912040a996c64851396f5922e4e7'>gnu</a>/<a href='/guix/log/gnu/system?id=690a347bdbb3912040a996c64851396f5922e4e7'>system</a>/<a href='/guix/log/gnu/system/locale.scm?id=690a347bdbb3912040a996c64851396f5922e4e7'>locale.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/system/locale.scm?id=690a347bdbb3912040a996c64851396f5922e4e7&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2023-09-16 15:35:25 +0200'>2023-09-16</span></td><td><a href='/guix/commit/gnu/system/locale.scm?id=f2cfb4a85c82882c571274573fd7ff646d380b63'>locale: Set %default-locale-definitions to glibc/hurd on the Hurd.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/system/locale.scm (%default-locale-libcs): Use only glib/hurd when
building on the Hurd.
</span></span></td><td>Janneke Nieuwenhuizen</td></tr>
<tr><td><span title='2023-04-19 16:32:03 +0200'>2023-04-19</span></td><td><a href='/guix/commit/gnu/system/locale.scm?id=4f4c38c881d4224dc545c82253d2a8f631f95927'>locale: Add glibc 2.33 to '%default-locale-libcs'.</a><span class='msg-avail'>...<span class='msg-tooltip'>Fixes &lt;https://issues.guix.gnu.org/62934&gt;.
Reported by Brian Cully &lt;bjc@spork.org&gt;.

* gnu/system/locale.scm (%default-locale-libcs): Add GLIBC-2.33.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-01-14 14:29:20 +0100'>2022-01-14</span></td><td><a href='/guix/commit/gnu/system/locale.scm?id=9d0d4b331d21cf555fdd6a8844d05389d934832c'>system: locale: Use only the current glibc.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/system/locale.scm (%default-locale-libcs): Remove glibc-2.31.
</span></span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2021-05-15 22:55:24 +0200'>2021-05-15</span></td><td><a href='/guix/commit/gnu/system/locale.scm?id=25487c3fe6a41dd62f6e53f256392224a3be2a08'>Merge branch 'master' into core-updates</a></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-05-04 14:19:11 +0200'>2021-05-04</span></td><td><a href='/guix/commit/gnu/system/locale.scm?id=2e4808465d7ea5cbff0486a515cd67e3370877ce'>locale: Remove glibc 2.29 from '%default-locale-libcs'.</a><span class='msg-avail'>...<span class='msg-tooltip'>Having 2.29 is most likely no longer justified.  Removing it reduces the
closure size returned by:

  guix size $(guix system build gnu/system/install.scm)

from 1.6G to 1.5G.

* gnu/system/locale.scm (%default-locale-libcs): Remove GLIBC-2.29.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-09-20 23:56:17 +0200'>2020-09-20</span></td><td><a href='/guix/commit/gnu/system/locale.scm?id=855bc05e118913ddc5d4c544a77a2f82c9df929c'>gnu: glibc: Add version 2.31.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/base.scm (glibc-2.31): New variable.
* gnu/system/locale.scm (%default-locale-libcs): Add it.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-08-26 18:45:28 +0200'>2020-08-26</span></td><td><a href='/guix/commit/gnu/system/locale.scm?id=6c443975c9cb94131f5956378495c6e3b627b6aa'>system: locale: Only use the current glibc.</a><span class='msg-avail'>...<span class='msg-tooltip'>Only use the current glibc, as adding glibc-2.29 for compatibility adds
~100MiB to the barebones system closure.

* gnu/system/locale.scm (%default-locale-libcs): Remove glibc-2.29.
</span></span></td><td>Mathieu Othacehe</td></tr>