zephyr: Add UTF8 kconfig to conditionally compile utf8.c

Add the kconfig option so that the utf8.c file can be
conditionally compile, and only for the applications
that need it.

Signed-off-by: Emil Gydesen <emil.gydesen@nordicsemi.no>

lib/os/CMakeLists.txt

@@ -24,7 +24,6 @@ zephyr_sources(
   heap-validate.c
   bitarray.c
   multi_heap.c
-  utf8.c
   )
 
 zephyr_sources_ifdef(CONFIG_CBPRINTF_COMPLETE cbprintf_complete.c)
@@ -48,6 +47,8 @@ zephyr_sources_ifdef(CONFIG_SHARED_MULTI_HEAP shared_multi_heap.c)
 
 zephyr_sources_ifdef(CONFIG_HEAP_LISTENER heap_listener.c)
 
+zephyr_sources_ifdef(CONFIG_UTF8 utf8.c)
+
 zephyr_library_include_directories(
   ${ZEPHYR_BASE}/kernel/include
   ${ZEPHYR_BASE}/arch/${ARCH}/include

lib/os/Kconfig

@@ -151,6 +151,12 @@ config REBOOT
 	  needed to perform a "safe" reboot (e.g. to stop the system clock before
 	  issuing a reset).
 
+config UTF8
+	bool "UTF-8 string operation supported"
+	help
+	  Enable the utf8 API. The API implements functions to specifically
+	  handle UTF-8 encoded strings.
+
 rsource "Kconfig.cbprintf"
 
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