Work around problems caused by limit on the length of the command line
in ld, which shows up when building OpenGL on Windows with SplitObjs=YES.

We now pass the names of the input files to ld via a linker script.
This is (probably) only supported by GNU ld, so we now have to detect
GNU ld in the configure script (yawn) and back off to the old method
if we don't have it.