don't build libbt-vendor when vendor/ is missing

Bug: 68817732
Change-Id: I301e1c1f65d7b71a4a1aaab978d4116f8f7a7864
Signed-off-by: Thierry Strudel <tstrudel@google.com>
diff --git a/Android.mk b/Android.mk
index cd2c3ae..da21c67 100644
--- a/Android.mk
+++ b/Android.mk
@@ -1,3 +1,5 @@
 ifeq ($(call is-vendor-board-platform,QCOM),true)
+ifneq ($(BUILD_WITHOUT_VENDOR),true)
 include $(call all-named-subdir-makefiles,libbt-vendor)
+endif
 endif # is-vendor-board-platform