package/perf: if libunwind is enabled, depend on it

Signed-off-by: Steven Noonan <steven@uplinklabs.net>
[Romain:
  - fix coding style]
Reviewed-by: Romain Naour <romain.naour@openwide.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/perf/perf.mk

@@ -36,6 +36,10 @@ ifeq ($(BR2_PACKAGE_SLANG),y)
 PERF_DEPENDENCIES += slang
 endif
 
+ifeq ($(BR2_PACKAGE_LIBUNWIND),y)
+PERF_DEPENDENCIES += libunwind
+endif
+
 ifeq ($(BR2_PACKAGE_NUMACTL),y)
 PERF_DEPENDENCIES += numactl
 endif