It seems like somewhere in the depths of convoluted includes an #include
of signal.h got dropped. Re-adding it makes the build succeed.
  dilfridge@gentoo.org

diff --git a/libsanitizer/asan/asan_linux.cc b/libsanitizer/asan/asan_linux.cc
index c504168b614..a2026621ca6 100644
--- a/libsanitizer/asan/asan_linux.cc
+++ b/libsanitizer/asan/asan_linux.cc
@@ -21,6 +21,7 @@
 #include "sanitizer_common/sanitizer_libc.h"
 #include "sanitizer_common/sanitizer_procmaps.h"
 
+#include <signal.h>
 #include <sys/time.h>
 #include <sys/resource.h>
 #include <sys/mman.h>