Add bccMarkExternalSymbol (to specify external symbol.)

By default libbcc will internalize every symbol, and perform
LTO.  However, in many situations we have to export a specific
function, such as "root" or "init" for RenderScript, so we are
adding bccMarkExternalSymbol.

Change-Id: I136eb8ff68e9ccf8c6595eb470f9718e1cb1e4ab
5 files changed