add ARC to newlib supported architectures

target/config/Config.in.libc

@@ -56,6 +56,7 @@ config ADK_TARGET_LIB_NEWLIB
 	select ADK_TARGET_WITHOUT_THREADS
 	depends on \
 		ADK_TARGET_ARCH_AARCH64 || \
+		ADK_TARGET_ARCH_ARC || \
 		ADK_TARGET_ARCH_ARM || \
 		ADK_TARGET_ARCH_BFIN || \
 		ADK_TARGET_ARCH_CRIS || \