perf/powerpc: Add support for unwinding perf-stackdump

Adds support for unwinding user stack dump by linking with libunwind.

Signed-off-by: Chandan Kumar <chandan.kumar@linux.vnet.ibm.com>
Reviewed-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Tested-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/tools/perf/config/Makefile b/tools/perf/config/Makefile
index eda1cfb..220536c 100644
--- a/tools/perf/config/Makefile
+++ b/tools/perf/config/Makefile
@@ -26,6 +26,7 @@
 # Additional ARCH settings for ppc
 ifeq ($(ARCH),powerpc)
   NO_PERF_REGS := 0
+  LIBUNWIND_LIBS := -lunwind -lunwind-ppc64
 endif
 
 # Additional ARCH settings for x86