package/libmemcached: force CMAKE_BUILD_TYPE

Force CMAKE_BUILD_TYPE to Release to avoid the following build failure
with c-icap or php-memcached raised since bump to version 1.1.4 and
switch to cmake-package in commit
7205df8a4f3c729b11a5f0c34885e6cf592f24b9:

Fixes:
 - http://autobuild.buildroot.org/results/bca84915550a72f1dc89c8661cba2545d6bc96ef
 - http://autobuild.buildroot.org/results/b140d225208e7fa44b935a119e74347caf710e55

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
[Peter: use +=]
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit d23bcbd2bb76fb157624d18e88ce33fd9a964fbe)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/libmemcached/libmemcached.mk

@@ -14,6 +14,10 @@ LIBMEMCACHED_LICENSE = BSD-3-Clause
 LIBMEMCACHED_LICENSE_FILES = LICENSE
 LIBMEMCACHED_CPE_ID_VENDOR = awesome
 
+# Force Release otherwise libraries will be suffixed by -dbg which will raise
+# unexpected build failures with packages that use libmemcached (e.g. c-icap)
+LIBMEMCACHED_CONF_OPTS += -DCMAKE_BUILD_TYPE=Release
+
 ifeq ($(BR2_PACKAGE_LIBEVENT),y)
 LIBMEMCACHED_DEPENDENCIES += libevent
 LIBMEMCACHED_CONF_OPTS += -DENABLE_MEMASLAP=ON