gpgrt-config: Portability fix for use of expr.
* src/gpgrt-config (sysroot): Care about possible interpretation of minus sign be considered an option to a program. (MAIN): Don't use 'match' of expr but use ':' instead.
- Reported-by: Roman Bogorodskiy <bogorodskiy@gmail.com>
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>