cygwin ld import library issue fix (removing unused "_nm_" symbols)

[DJ Delorie]

> Well - personally I thought you had gcc to support all your
> platforms, which for ages has supported either style of
> comment... there's only a few relics I've run across which were
> barely even functional as compilers that didn't support it :)

gcc and binutils are the two packages that are at the highest
portability levels.  Other packages may choose to require those two be
ported first.  Binutils does not require that gcc be ported before it.
In fact, gcc sometimes requires that binutils be ported first,
otherwise it cannot build libgcc.a