libpayload: Don't leave temporary files behind

For some reason the rm -f didn't quite work on my system,
but sending gcc output to /dev/null does.

Change-Id: I7ece9aa9abe564bbc646ae53df1d3cd0c5aa84a2
Signed-off-by: Patrick Georgi <patrick.georgi@secunet.com>
Reviewed-on: http://review.coreboot.org/1543
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: Anton Kochkov <anton.kochkov@gmail.com>

payloads/libpayload/bin/lpgcc

@@ -58,10 +58,8 @@ BASE=`dirname $0`
 _LDSCRIPT="-Wl,-T,$_LIBDIR/libpayload.ldscript"
 
 trygccoption() {
-	$DEFAULT_CC $1 -S -xc /dev/null -o .$$.tmp &> /dev/null
-	RET=$?
-	rm -f .$$.tmp
-	return $RET
+	$DEFAULT_CC $1 -S -xc /dev/null -o /dev/null &> /dev/null
+	return $?
 }
 
 DEBUGME=0