Missing include needed for ports-gcc to have raise in scope

Index: googletest/src/gtest.cc
--- googletest/src/gtest.cc.orig
+++ googletest/src/gtest.cc
@@ -44,6 +44,7 @@
 #include <chrono>  // NOLINT
 #include <cmath>
 #include <cstdint>
+#include <csignal>
 #include <cstdlib>
 #include <cstring>
 #include <initializer_list>