Make host-libpcap dependency for waveguide only.

gflt110 build was failing on my workstation when building
host-libpcap, due to unsatisfied libnl (<netlink/>) dependency. libnl
in turn wouldn't build because of unsatisfied glib2 dependency. glib2
wouldn't build at all on the gflt110.

Turns out host-libpcap is only needed for waveguide. Waveguide is not
built on gflt110.

So this CL makes it so host-libpcap is built only if waveguide is
getting built.

Change-Id: If336f0215ca75e3a3bd78030d0eefa768bee60d3
diff --git a/package/google/google_platform/google_platform.mk b/package/google/google_platform/google_platform.mk
index bbe4899..b660253 100644
--- a/package/google/google_platform/google_platform.mk
+++ b/package/google/google_platform/google_platform.mk
@@ -32,8 +32,7 @@
 HOST_GOOGLE_PLATFORM_DEPENDENCIES=\
 	$(GOOGLE_PLATFORM_DEPENDENCIES) \
 	host-googletest \
-	host-protobuf \
-	host-libpcap
+	host-protobuf
 
 GOOGLE_PLATFORM_TARGET_CFLAGS=-I$(STAGING_DIR)/usr/include/python2.7
 GOOGLE_PLATFORM_HOST_CFLAGS=-isystem $(HOST_DIR)/usr/include
@@ -101,6 +100,7 @@
 endif
 
 ifeq ($(BR2_PACKAGE_GOOGLE_PLATFORM_WAVEGUIDE),y)
+HOST_GOOGLE_PLATFORM_DEPENDENCIES += host-libpcap
 BUILD_WAVEGUIDE=y
 endif