[libc] Add localtime_r to baremetal entrypoints

Author: Prabhuk

libc/config/baremetal/arm/entrypoints.txt

@@ -269,6 +269,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.time.difftime
     libc.src.time.gmtime
     libc.src.time.gmtime_r
+    libc.src.time.localtime_r
     libc.src.time.mktime
     libc.src.time.strftime
     libc.src.time.strftime_l