zigbee: kconfig: use minimal libc by default

Zigbee samples have some dependencies on minimal libc implementation.

For instance, RAM Power Down library usage leads to a bus fault when
using Picolib.

Signed-off-by: Eduardo Montoya <eduardo.montoya@nordicsemi.no>

Author: edmont

samples/zigbee/light_switch/child_image/mcuboot/boards/nrf5340dk_nrf5340_cpuapp_fota.conf

@@ -38,6 +38,3 @@ CONFIG_FPROTECT=y
 CONFIG_NORDIC_QSPI_NOR=y
 CONFIG_NORDIC_QSPI_NOR_FLASH_LAYOUT_PAGE_SIZE=4096
 CONFIG_NORDIC_QSPI_NOR_STACK_WRITE_BUFFER_SIZE=16
-
-# Use minimal C library instead of the Picolib
-CONFIG_MINIMAL_LIBC=y

subsys/zigbee/Kconfig

@@ -27,6 +27,13 @@ if ZIGBEE
 
 rsource "lib/Kconfig"
 
+# Override libc implementation
+choice LIBC_IMPLEMENTATION
+	default MINIMAL_LIBC
+	help
+	  Use minimal libc implementation with Zigbee.
+endchoice
+
 config NET_L2_ZIGBEE
 	bool "Zigbee L2"
 	depends on NETWORKING