Simplify process exit-code handling on Posix, take 2.

runtime/bin/platform_linux.cc

Index: runtime/bin/platform_linux.cc
diff --git a/runtime/bin/platform_linux.cc b/runtime/bin/platform_linux.cc
index 4a70ee5821d1ab95747c1af43ab799c137a03c73..af557af9bead2b39afea05d69cec8f32443409e3 100644
--- a/runtime/bin/platform_linux.cc
+++ b/runtime/bin/platform_linux.cc
@@ -26,14 +26,6 @@ bool Platform::Initialize() {
     perror("Setting signal handler failed");
     return false;
   }
-  // Unblock SIGCHLD as waiting on spawned child process depends
-  // on successful interception of this signal.
-  sigset_t newset;
-  sigemptyset(&newset);
-  sigaddset(&newset, SIGCHLD);
-  if (sigprocmask(SIG_UNBLOCK, &newset, NULL) != 0) {
-    perror("Unblocking SIGCHLD signal failed");
-  }
   return true;
 }