strace: fix legal info

The license file changed from COPYRIGHT->COPYING. Fixes:
http://autobuild.buildroot.net/results/b61/b61e1775cd1eec83470424e88ced5bd49e0cd469/

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/strace/strace.mk

@@ -8,7 +8,7 @@ STRACE_VERSION = 4.8
 STRACE_SOURCE = strace-$(STRACE_VERSION).tar.xz
 STRACE_SITE = http://downloads.sourceforge.net/project/strace/strace/$(STRACE_VERSION)
 STRACE_LICENSE = BSD-3c
-STRACE_LICENSE_FILES = COPYRIGHT
+STRACE_LICENSE_FILES = COPYING
 
 STRACE_CONF_ENV = ac_cv_header_linux_if_packet_h=yes \
 		  ac_cv_header_linux_netlink_h=yes