PRODUCT_PACKAGES: change all places to be appended

with the "+=" operation, instead of the overwriting
operation of ":=", to avoid unexpected build errors
when inherit-product from other files.

Bug: 265084621
Test: build db845c successfully

Change-Id: Id0e7e444af2069b34bb36245163aac9799e6e3d1
Signed-off-by: Yongqin Liu <yongqin.liu@linaro.org>
diff --git a/rb5/device.mk b/rb5/device.mk
index 8fc29a5..6f4f75a 100644
--- a/rb5/device.mk
+++ b/rb5/device.mk
@@ -25,7 +25,7 @@
     $(LOCAL_PATH)/mixer_paths.xml:$(TARGET_COPY_OUT_VENDOR)/etc/mixer_paths.xml \
 
 # Build generic Audio HAL
-PRODUCT_PACKAGES := audio.primary.rb5
+PRODUCT_PACKAGES += audio.primary.rb5
 
 # BootControl HAL
 PRODUCT_PACKAGES += \