kFreeBSD has stub utimensat() up to version 9.  Without
this change qemu configure "thinks" that the system has
utimensat support and tries to use (CPP) symbols which
comes in system headers together with utimensat(),
namely UTIME_OMIT and UTIME_NOW, but thoes are not
defined.

The same applies to pipe2() call.

--- a/configure
+++ b/configure
@@ -3135,6 +3135,14 @@ cat > $TMPC << EOF
 #include <fcntl.h>
 #include <sys/stat.h>
 
+#if defined __stub_futimens || defined __stub___futimens
+choke me
+#endif
+
+#if defined __stub_utimensat || defined __stub___utimensat
+choke me
+#endif
+
 int main(void)
 {
     utimensat(AT_FDCWD, "foo", NULL, 0);
@@ -3152,6 +3161,10 @@ cat > $TMPC << EOF
 #include <unistd.h>
 #include <fcntl.h>
 
+#if defined __stub_pipe2 || defined __stub___pipe2
+choke me
+#endif
+
 int main(void)
 {
     int pipefd[2];