Build system support to export include paths

Bug: 5573756
With this change, we can set LOCAL_EXPORT_C_INCLUDE_DIRS in the module
definition to export include dir paths.
Paths in LOCAL_EXPORT_C_INCLUDE_DIRS should be relative to the top dir
of the source tree.
If a library (shared or static) exports some include paths, any module
using it will import the include paths and add them to the compiler
command line.

Change-Id: I49aabc589d2cf214044d13ccd5532ef68209adf0
diff --git a/core/host_static_library.mk b/core/host_static_library.mk
index 39c99ee..b04291b 100644
--- a/core/host_static_library.mk
+++ b/core/host_static_library.mk
@@ -13,6 +13,9 @@
 ifeq ($(strip $(LOCAL_MODULE_SUFFIX)),)
 LOCAL_MODULE_SUFFIX := .a
 endif
+ifneq ($(strip $(LOCAL_MODULE_STEM)$(LOCAL_BUILT_MODULE_STEM)),)
+$(error $(LOCAL_PATH): Can not set module stem for a library)
+endif
 LOCAL_UNINSTALLABLE_MODULE := true
 
 LOCAL_IS_HOST_MODULE := true