runtime: set library name based on compiler name

runtime: set library name based on compiler name

Different compilers may have different release cadences or ABI
incompatibilities, so it does not make sense to use the same library
name for runtime libraries intended for different compilers.

This CL causes a libgo built by llgo to receive the name libgo-llgo.
Likewise, libgobegin is named libgobegin-llgo.

From-SVN: r217583