perf build: Disable libdw DWARF unwind when built with NO_DWARF

We get a linker error if we try to build with NO_DWARF since we build
util/unwind-libdw.c, but do not include -ldw

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1430306131-6780-1-git-send-email-naveen.n.rao@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/config/Makefile b/tools/perf/config/Makefile
index 435b6ca..1b957a1 100644
--- a/tools/perf/config/Makefile
+++ b/tools/perf/config/Makefile
@@ -268,6 +268,10 @@
   endif # libelf support
 endif # NO_LIBELF
 
+ifdef NO_DWARF
+  NO_LIBDW_DWARF_UNWIND := 1
+endif
+
 ifndef NO_LIBELF
   CFLAGS += -DHAVE_LIBELF_SUPPORT
   EXTLIBS += -lelf