package/gflags: force Release mode

Force Release otherwise libraries will be suffixed by _debug which will raise
unexpected build failures with packages that use gflags (e.g. rocksdb)

Fixes:
 - http://autobuild.buildroot.org/results/3545774258babc3584f69e7d523efdf7fff1acb5

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit 198e42d6ebdc9a55da8378e437f3e4c20678b94b)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/gflags/gflags.mk

@@ -10,8 +10,12 @@ GFLAGS_INSTALL_STAGING = YES
 GFLAGS_LICENSE = BSD-3-Clause
 GFLAGS_LICENSE_FILES = COPYING.txt
 
+# Force Release otherwise libraries will be suffixed by _debug which will raise
+# unexpected build failures with packages that use gflags (e.g. rocksdb)
+GFLAGS_CONF_OPTS = -DCMAKE_BUILD_TYPE=Release
+
 ifeq ($(BR2_TOOLCHAIN_HAS_THREADS),)
-GFLAGS_CONF_OPTS = -DBUILD_gflags_LIB=OFF \
+GFLAGS_CONF_OPTS += -DBUILD_gflags_LIB=OFF \
 	-DCMAKE_CXX_FLAGS="$(TARGET_CXXFLAGS) -DNO_THREADS"
 endif