Build newlib library to be thread-safe in multithreaded environment.

https://github.com/zephyrproject-rtos/zephyr/pull/21518
https://github.com/zephyrproject-rtos/zephyr/issues/21519
https://github.com/zephyrproject-rtos/zephyr/pull/36201

https://sourceware.org/legacy-ml/newlib/2016/msg01165.html
https://sourceware.org/git/?p=newlib-cygwin.git;a=commit;h=bd54749095ee45d7136b6e7c8a1e5218749c87b6

Error log:
newlib/libc-hooks.c:310:1: note: in expansion of macro 'BUILD_ASSERT'
BUILD_ASSERT(IS_ENABLED(_RETARGETABLE_LOCKING), "Retargetable locking must be enabled");

Signed-off-by: Naveen Saini <naveen.kumar.saini@...>
---
meta-zephyr-core/recipes-core/newlib/newlib_%.bbappend | 5 +++++
1 file changed, 5 insertions(+)
create mode 100644 meta-zephyr-core/recipes-core/newlib/newlib_%.bbappend

diff --git a/meta-zephyr-core/recipes-core/newlib/newlib_%.bbappend b/meta-zephyr-core/recipes-core/newlib/newlib_%.bbappend
new file mode 100644
index 0000000..1a20b06
--- /dev/null
+++ b/meta-zephyr-core/recipes-core/newlib/newlib_%.bbappend
@@ -0,0 +1,5 @@
+# BUILD_ASSERT(IS_ENABLED(_RETARGETABLE_LOCKING), "Retargetable locking must be enabled");
+
+EXTRA_OECONF:append = " \
+ --enable-newlib-retargetable-locking \
+ "
--
2.25.1