Just for info:
I've succeded upgrading to binutils 2.15 (from pure binutils source) on the mingw platform, through almost automatically configuring, compiling and installing dmake and perl.
However, the LLVM configure searches a nonexistent path (c:/mingw/mingw32/bin) in the PATH environment and funny enough finds an old version of ld. So, you have to manually fix the llvm libtool script to reference to your upgraded ld.
The reloc problem is fixed in binutils