initialize pid cache in startup

Author: Yifan Zhu

libc/startup/linux/CMakeLists.txt

@@ -101,6 +101,7 @@ add_object_library(
     libc.include.llvm-libc-macros.link_macros
     libc.src.__support.threads.thread
     libc.src.__support.OSUtil.osutil
+    libc.src.__support.OSUtil.pid
     libc.src.stdlib.exit
     libc.src.stdlib.atexit
     libc.src.unistd.environ

libc/startup/linux/do_start.cpp

@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 #include "startup/linux/do_start.h"
 #include "include/llvm-libc-macros/link-macros.h"
+#include "src/__support/OSUtil/pid.h"
 #include "src/__support/OSUtil/syscall.h"
 #include "src/__support/threads/thread.h"
 #include "src/stdlib/atexit.h"
@@ -64,6 +65,7 @@ static ThreadAttributes main_thread_attrib;
   auto tid = syscall_impl<long>(SYS_gettid);
   if (tid <= 0)
     syscall_impl<long>(SYS_exit, 1);
+  ProcessIdentity::refresh_cache();
   main_thread_attrib.tid = static_cast<int>(tid);
 
   // After the argv array, is a 8-byte long NULL value before the array of env