ARC: Enable OBSTACK in defconfig for ARC

OBSTACK is required for native builds of binutils and GDB.

Signed-off-by: Anton Kolesov <Anton.Kolesov@synopsys.com>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

extra/Configs/defconfigs/arc/defconfig

@@ -8,6 +8,7 @@ LDSO_RUNPATH=y
 # LDSO_SAFE_RUNPATH is not set
 UCLIBC_HAS_THREADS_NATIVE=y
 PTHREADS_DEBUG_SUPPORT=y
+UCLIBC_HAS_OBSTACK=y
 UCLIBC_SUSV2_LEGACY=y
 UCLIBC_SUSV3_LEGACY=y
 UCLIBC_SUSV4_LEGACY=y