package/rtl_433: force Release build

Force Release build to avoid the following build failure which is raised
since the addition of the package in commit
4634e84978a3e64e9050021d209a41cd88a1ad16:

/tmp/instance-3/output-1/host/opt/ext-toolchain/bin/../lib/gcc/i586-buildroot-linux-musl/9.3.0/../../../../i586-buildroot-linux-musl/bin/ld: cannot find -lasan
/tmp/instance-3/output-1/host/opt/ext-toolchain/bin/../lib/gcc/i586-buildroot-linux-musl/9.3.0/../../../../i586-buildroot-linux-musl/bin/ld: cannot find -lubsan

Fixes:
 - http://autobuild.buildroot.org/results/83274082879f9599bc106e12a253f4b9229ea00b

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

package/rtl_433/rtl_433.mk

@@ -9,7 +9,9 @@ RTL_433_SITE = $(call github,merbanan,rtl_433,$(RTL_433_VERSION))
 RTL_433_LICENSE = GPL-2.0+
 RTL_433_LICENSE_FILES = COPYING
 
+# Force Release build to remove ASAN.
 RTL_433_CONF_OPTS = \
+	-DCMAKE_BUILD_TYPE=Release \
 	-DBUILD_DOCUMENTATION=OFF \
 	-DBUILD_TESTING=OFF \
 	-DBUILD_TESTING_ANALYZER=OFF \