clock_nanosleep: add CLOCK_THREAD_CPUTIME_ID special case

POSIX makes "the CPU-time clock of the calling thread" (i.e.,
CLOCK_THREAD_CPUTIME_ID) a special case which returns EINVAL instead of
ENOTSUP.

However, the clock_nanosleep syscall treats this clock just like any
other, and returns -EOPNOTSUPP to indicate an unimplemented nanosleep
handler.  So we need to handle this ourselves in userspace.

This change fixes the LTP clock_nanosleep01 testcase.

Change-Id: If3bed940d276834bcd114d8c17f96197e9384711
Signed-off-by: Greg Hackmann <ghackmann@google.com>
diff --git a/libc/bionic/clock_nanosleep.cpp b/libc/bionic/clock_nanosleep.cpp
index 8e2146f..eade850 100644
--- a/libc/bionic/clock_nanosleep.cpp
+++ b/libc/bionic/clock_nanosleep.cpp
@@ -33,6 +33,8 @@
 extern "C" int ___clock_nanosleep(clockid_t, int, const timespec*, timespec*);
 
 int clock_nanosleep(clockid_t clock_id, int flags, const timespec* in, timespec* out) {
+  if (clock_id == CLOCK_THREAD_CPUTIME_ID) return EINVAL;
+
   ErrnoRestorer errno_restorer;
   return (___clock_nanosleep(clock_id, flags, in, out) == 0) ? 0 : errno;
 }