Always wrap waitpid in TEMP_FAILURE_RETRY.

Strictly not needed in the WNOHANG case, but it's probably best to have
every waitpid wrapped for future copy & pasters.

Bug: https://issuetracker.google.com/69525592
Test: ran tests
Change-Id: I013b0a52d2753e3d32638e9b84c79af7327fb405
diff --git a/tests/gtest_main.cpp b/tests/gtest_main.cpp
index 3f59a9c..33dbfd9 100644
--- a/tests/gtest_main.cpp
+++ b/tests/gtest_main.cpp
@@ -324,7 +324,7 @@
   }
 
   int status;
-  if (waitpid(pid, &status, 0) != pid) {
+  if (TEMP_FAILURE_RETRY(waitpid(pid, &status, 0)) != pid) {
     perror("waitpid");
     return false;
   }