Disallow setting LOCAL_MODULE_STEM for android packages

LOCAL_MODULE_STEM is not used in the packaging code,
except when setting PACKAGES.$(LOCAL_MODULE).STEM.
Having this disconnect between PACKAGES.$(LOCAL_MODULE).STEM
and the actual name of the apk causes an apk signing
step to fail.

Other module types like BUILD_HEADER_LIBRARY explicetly
disallow setting LOCAL_MODULE_STEM, so we can also just
do that for packages.

Fixes: 204027319
Test: Presubmits
Change-Id: Ib3da9a8dd6792a6c9d725cb24b835b32dbb13c40
diff --git a/core/package_internal.mk b/core/package_internal.mk
index 9f5a599..800dbbc 100644
--- a/core/package_internal.mk
+++ b/core/package_internal.mk
@@ -35,6 +35,10 @@
 endif
 LOCAL_MODULE_SUFFIX := $(COMMON_ANDROID_PACKAGE_SUFFIX)
 
+ifneq ($(strip $(LOCAL_MODULE_STEM)$(LOCAL_BUILT_MODULE_STEM)),)
+$(error $(LOCAL_PATH): Package modules may not define LOCAL_MODULE_STEM or LOCAL_BUILT_MODULE_STEM)
+endif
+
 ifneq ($(strip $(LOCAL_MODULE)),)
 $(error $(LOCAL_PATH): Package modules may not define LOCAL_MODULE)
 endif