tests: lib: mem_alloc: Fix incorrect newlib variant usage

NEWLIB_LIBC_NANO defaults to y when building with a toolchain that
supports nano.specs and this was causing the libraries.libc.newlib
test to link with the newlib nano variant (libc_nano.a) when it should
be linking with the normal newlib (libc.a).

By setting CONFIG_NEWLIB_LIBC_NANO=n in prj_newlib.conf, we make sure
that the libraries.libc.newlib test links with the normal newlib.

For more details, refer to the issue #21167.

Signed-off-by: Stephanos Ioannidis <[email protected]>

Author: stephanosio

tests/lib/mem_alloc/prj_newlib.conf

@@ -1,4 +1,5 @@
 CONFIG_ZTEST=y
 CONFIG_NEWLIB_LIBC=y
+CONFIG_NEWLIB_LIBC_NANO=n
 CONFIG_NEWLIB_LIBC_ALIGNED_HEAP_SIZE=512
 CONFIG_TEST_USERSPACE=y