Add GNU libc extension variables __progname and __progname_full

This patch adds GNU libc extension variables __progname and __progname_full
used by coreutils. These seem to come from BSD as 'BSD' paragraph
explains - https://rosettacode.org/wiki/Program_name#C.

Signed-off-by: Waldemar Kozaczuk <[email protected]>
Message-Id: <[email protected]>

Author: wkozaczuk

libc/libc.cc

@@ -32,6 +32,9 @@
 char *program_invocation_name;
 char *program_invocation_short_name;
 
+weak_alias(program_invocation_name, __progname_full);
+weak_alias(program_invocation_short_name, __progname);
+
 int libc_error(int err)
 {
     errno = err;