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>
ected='selected'>koszko</option>
<option value='koszko-scripts'>koszko-scripts</option>
</select> <input type='submit' value='switch'/></form></td></tr>
<tr><td class='sub'>Wojtek's customized Guix</td><td class='sub right'></td></tr></table>
<table class='tabs'><tr><td>
<a href='/guix/about/'>about</a><a href='/guix/'>summary</a><a href='/guix/refs/?id=f8d0f7de2d75e88cf882db10bffc1604a8af4bca'>refs</a><a class='active' href='/guix/log/gnu/packages/inklingreader.scm'>log</a><a href='/guix/tree/gnu/packages/inklingreader.scm?id=f8d0f7de2d75e88cf882db10bffc1604a8af4bca'>tree</a><a href='/guix/commit/gnu/packages/inklingreader.scm?id=f8d0f7de2d75e88cf882db10bffc1604a8af4bca'>commit</a><a href='/guix/diff/gnu/packages/inklingreader.scm?id=f8d0f7de2d75e88cf882db10bffc1604a8af4bca'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/packages/inklingreader.scm'>
<input type='hidden' name='id' value='f8d0f7de2d75e88cf882db10bffc1604a8af4bca'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=f8d0f7de2d75e88cf882db10bffc1604a8af4bca'>root</a>/<a href='/guix/log/gnu?id=f8d0f7de2d75e88cf882db10bffc1604a8af4bca'>gnu</a>/<a href='/guix/log/gnu/packages?id=f8d0f7de2d75e88cf882db10bffc1604a8af4bca'>packages</a>/<a href='/guix/log/gnu/packages/inklingreader.scm?id=f8d0f7de2d75e88cf882db10bffc1604a8af4bca'>inklingreader.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/packages/inklingreader.scm?id=f8d0f7de2d75e88cf882db10bffc1604a8af4bca&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2024-05-21 08:54:00 +0300'>2024-05-21</span></td><td><a href='/guix/commit/gnu/packages/inklingreader.scm?id=246a118767911fd801f3acbf522c1891185460d0'>gnu: inklingreader: Build with librsvg-for-system.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/inklingreader.scm (inklingreader)[inputs]: Replace
librsvg with librsvg-for-system.

Change-Id: I2cf3d3fbed982f199b94f847b75c6c49472d9b4a
</span></span></td><td>Efraim Flashner</td></tr>