build: remove clang warning about global var 'match'

remove clang warning - "Argument to free() is the address of a global
variable, which is not memory allocated by malloc()".

Change-Id: I015273eafc9644207684b363434c6ae8149bfcde
Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-on: http://openocd.zylin.com/1613
Tested-by: jenkins