Really fix the readonly source case

Some libraries were already only using the headers through
LOCAL_EXPORT_C_INCLUDE_DIRS, which meant when I stopped generating it
in the source tree, they no longer had access to it. My local testing
didn't catch it because I had a stale version in my source tree hidden
with a .gitignore entry.

Instead, generate this file into the generated sources directory for
libva, export that include path as well, then set it up to be copied
into the global header directory.

Change-Id: If2aa8ea443ddb81e7f7a9dc2d7b2f5363c6e4fd0
3 files changed