utimes: Export utimensat based utimes

sys/time.h has libc_hidden_proto(utimes) which generates the hidden
"__GI_utimes" symbol reference, and common/utimes.c has a
libc_hidden_def(utimes) which generates the exported "utimes" alias.

As part of no-legacy-syscall kernel ABI, Commit 80dc2ed05
"utimes: Use utimensat if arch does not have the utimes syscall"
introduced a new wrapper, but missed the corresponding libc_hidden_def,
causing Busybox (1.20.0) link to fail (for ARC).

Also don't generate a STUB, in that case.
---------------->8-------------------
....
touch.c:(.text.touch_main+0xdc): undefined reference to `utimes'
touch.c:(.text.touch_main+0x114): undefined reference to `utimes'
libbb/lib.a(copy_file.o): In function `copy_file':
copy_file.c:(.text.copy_file+0x446): undefined reference to `utimes'
collect2: ld returned 1 exit status
---------------->8-------------------

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Cc: Markos Chandras <markos.chandras@imgtec.com>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

libc/sysdeps/linux/common/stubs.c

@@ -448,10 +448,12 @@ make_stub(lutimes)
 # endif
 #endif
 
+#ifndef __NR_utimensat
 #if !defined __NR_utime && !defined __NR_utimes
 /*make_stub(utime) obsoleted */
 make_stub(utimes)
 #endif
+#endif
 
 #if !defined __NR_umount && !defined __NR_umount2 && defined __UCLIBC_LINUX_SPECIFIC__
 make_stub(umount)

libc/sysdeps/linux/common/utimes.c

@@ -51,6 +51,6 @@ int utimes(const char *file, const struct timeval tvp[2])
 }
 #endif
 
-#if defined __NR_utimes || defined __NR_utime
+#if defined __NR_utimensat || defined __NR_utimes || defined __NR_utime
 libc_hidden_def(utimes)
 #endif