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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<tr><td><span title='2023-05-18 23:10:56 -0400'>2023-05-18</span></td><td><a href='/guix/commit/gnu/tests/rsync.scm?id=03e601da49e43ed0235144f32095ce5f58f16275'>services: rsync: Use make-inetd-constructor.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/rsync.scm (rsync-shepherd-service): Use make-inetd-constructor
if available in start slot.
* gnu/tests/rsync.scm (run-rsync-test): Delete "PID file" test.

Reviewed-by: Ludovic Courtès &lt;ludo@gnu.org&gt;
</span></span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2021-12-23 16:05:13 +0100'>2021-12-23</span></td><td><a href='/guix/commit/gnu/tests/rsync.scm?id=2a49ddb513476cd45ebca618ffb0b9e381c1e497'>tests: rsync: Fix it.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/tests/rsync.scm ("Test file not copied to read-only share"): This
returns the error code 1 and not 10.
</span></span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2021-12-21 15:47:04 +0100'>2021-12-21</span></td><td><a href='/guix/commit/gnu/tests/rsync.scm?id=3b3bef3e4e3a8f38e8686262cd12e1786a9ac2b0'>tests: rsync: Define several modules.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/tests/rsync.scm (run-rsync-test)["Test file not copied to
read-only share", "Test file correctly received from read-only share"]:
New tests.
(%rsync-os): Define two modules.
</span></span></td><td>Ludovic Courtès</td></tr>