vendor: allow choosing Lawnchair or Trebuchet as launcher at build time

 * Introduces TARGET_USES_LAWNCHAIR device option
 * If set to true, also override config_recentsComponentName in your DT and set it to ch.deletescape.lawnchair.ci/com.android.quickstep.RecentsActivity

Change-Id: Iddda81db8979f514fd7afc59fb5b70c7d6295ed2
diff --git a/prebuilt/common/Android.mk b/prebuilt/common/Android.mk
index 38de312..dcf89b2 100644
--- a/prebuilt/common/Android.mk
+++ b/prebuilt/common/Android.mk
@@ -130,6 +130,7 @@
 LOCAL_PRODUCT_MODULE := true
 include $(BUILD_PREBUILT)
 
+ifeq ($(TARGET_USES_LAWNCHAIR),true)
 include $(CLEAR_VARS)
 LOCAL_MODULE := Lawnchair
 LOCAL_SRC_FILES := priv-app/$(LOCAL_MODULE).apk
@@ -141,6 +142,7 @@
 LOCAL_DEX_PREOPT := false
 LOCAL_REPLACE_PREBUILT_APK_INSTALLED := $(LOCAL_PATH)/$(LOCAL_SRC_FILES)
 include $(BUILD_PREBUILT)
+endif
 
 include $(CLEAR_VARS)
 LOCAL_MODULE := Longshot