WIP: builds (but displys nothing) on Linux

This is very much WIP, but I wanted to open some discussion and make sure I don't go too far down any wrong paths.

So far, this patch:

 - adds stubs for `inspectable_web_contents_view_linux`
 - adds `CFLAGS+=-fno-rtti` to match the apparent build options on libchromiumcontent.  Otherwise we get lots of typeinfo missing errors.
 - adds libchromiumcontent.so to the required libraries