[compiler-rt] Fix build of Sanitizer-Test_Nolibc after D80648

Running ninja check-sanitizer fails for after that patch (commit
058f5f6) with the following error:

libRTSanitizerCommon.test.nolibc.x86_64.a(sanitizer_posix.cpp.o): In
function `__sanitizer::GetNamedMappingFd(char const*, unsigned long,
int*)':
..../llvm-project/compiler-rt/lib/sanitizer_common/sanitizer_posix.cpp:358:
undefined reference to `fcntl'
clang-12: error: linker command failed with exit code 1 (use -v to see
invocation)

This patch works around the problem by only calling fcntl if O_CLOEXEC
is not defined.

Reviewed By: plopresti

Differential Revision: https://reviews.llvm.org/D85114

Author: arichardson

compiler-rt/lib/sanitizer_common/sanitizer_posix.cpp

@@ -354,11 +354,11 @@ int GetNamedMappingFd(const char *name, uptr size, int *flags) {
   int fd = ReserveStandardFds(
       internal_open(shmname, O_RDWR | O_CREAT | O_TRUNC | o_cloexec, S_IRWXU));
   CHECK_GE(fd, 0);
-  if (!o_cloexec) {
-    int res = fcntl(fd, F_SETFD, FD_CLOEXEC);
-    CHECK_EQ(0, res);
-  }
   int res = internal_ftruncate(fd, size);
+#if !defined(O_CLOEXEC)
+  res = fcntl(fd, F_SETFD, FD_CLOEXEC);
+  CHECK_EQ(0, res);
+#endif
   CHECK_EQ(0, res);
   res = internal_unlink(shmname);
   CHECK_EQ(0, res);