toolchain: Fix glibc selection on ARC targets

Without this change no libc is selected and the build will fail. This
will select glibc for ARC CPUs.

Fixes: 95f1002acab5 ("toolchain: default to glibc for ARC")
Signed-off-by: Hauke Mehrtens <[email protected]>

toolchain/Config.in

@@ -260,6 +260,7 @@ config GDB
 	  Enable if you want to build the gdb.
 
 config USE_GLIBC
+	default y if !TOOLCHAINOPTS && !EXTERNAL_TOOLCHAIN && !NATIVE_TOOLCHAIN && (arc)
 	bool
 
 config USE_MUSL