android: make libbacktrace optional on USE_LIBBACKTRACE

Otherwise with VNDK enabled we fail linking:
   src/gallium/targets/dri/Android.mk: error: gallium_dri (native:vendor)
   should not link to libbacktrace.vendor (native:vndk_private)

Option makes it possible to use libbacktrace only when VNDK is not
enabled.

Signed-off-by: Tapani Pälli <tapani.palli@intel.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>

src/gallium/auxiliary/Android.mk

@@ -32,8 +32,11 @@ LOCAL_SRC_FILES := \
 	$(C_SOURCES) \
 	$(NIR_SOURCES) \
 	$(RENDERONLY_SOURCES) \
-	$(VL_STUB_SOURCES) \
-	util/u_debug_stack_android.cpp
+	$(VL_STUB_SOURCES)
+
+ifeq ($(USE_LIBBACKTRACE),true)
+	LOCAL_SRC_FILES += util/u_debug_stack_android.cpp
+endif
 
 LOCAL_C_INCLUDES := \
 	$(GALLIUM_TOP)/auxiliary/util \

src/gallium/targets/dri/Android.mk

@@ -40,12 +40,15 @@ LOCAL_LDFLAGS := \
 	-Wl,--undefined-version
 
 LOCAL_SHARED_LIBRARIES := \
-	libbacktrace \
 	libdl \
 	libglapi \
 	libexpat \
 	libz
 
+ifeq ($(USE_LIBBACKTRACE),true)
+	LOCAL_SHARED_LIBRARIES += libbacktrace
+endif
+
 $(foreach d, $(MESA_BUILD_GALLIUM), $(eval LOCAL_CFLAGS += $(patsubst HAVE_%,-D%,$(d))))
 
 # sort GALLIUM_LIBS to remove any duplicates