Seldom the test instrprof-gcov-fork.test is failing, so:
- add an O_EXCL when trying to create the file to avoid a race condition;
- add an error message when the locking is failing.
The failure is:
--
/b/sanitizer-x86_64-linux/build/llvm/projects/compiler-rt/test/profile/Posix/../Inputs/instrprof-gcov-fork.c.gcov:10:15: error: CHECK-NEXT: expected string not found in input
// CHECK-NEXT:function func2 called 2 returned 100% blocks executed 100%
^
instrprof-gcov-fork.c.gcov:10:1: note: scanning from here
function func2 called 1 returned 100% blocks executed 100%
^
In this test we call func2 after having forked so it should be called two times (in the parent process and in the cihld process)