[lto][plugin] How to find libc?

[Rafael Espindola]

Ian noted that when linking libc statically into a program and using
the gold plugin, we have to ask gold to rescan libc. The problem is,
gcc normally doesn't know which libc is being used. It will just pass
-lc to the linker and the linker searches for it.

On way to fix this is to implement the same algorithms used in the
linker in gcc.

Another way is to add a new callback into gold: add_input_library. It
would be similar to add_input_file, but the linker would search for
library. With this callback we would be able to do

-pass-through=libgcc.a -pass-through=-lc

Opinions? Suggestions?

Thanks,
-- 
Rafael Ávila de Espíndola