perf trace/scripting: Silence PERL_EMBED_* backtick errors

The backtick shell substitutions for PERL_EMBED_LDOPT/CCOPT make
a lot of noise on stderr if Embed.pm isn't installed - this
silences them.

Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
Cc: fweisbec@gmail.com
Cc: rostedt@goodmis.org
Cc: anton@samba.org
Cc: hch@infradead.org
LKML-Reference: <1259565529-6407-2-git-send-email-tzanussi@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>