zephyr: add dependency on full libc++

See https://github.com/zephyrproject-rtos/zephyr/pull/52946 for
additional information about the changes to C++ support.

Change-Id: If153785bab8794ab3d5f1c0ae0da7b6db572ac13
diff --git a/platform/zephyr/Kconfig b/platform/zephyr/Kconfig
index eae630c..e656ee3 100644
--- a/platform/zephyr/Kconfig
+++ b/platform/zephyr/Kconfig
@@ -6,6 +6,7 @@
 
 menuconfig CHRE
 	bool "CHRE Support"
+	select REQUIRES_FULL_LIBCPP
 	help
 	  This option enables the CHRE library.