After some more reflection (and no negative feedback), I am reverting the
original patch and applying my version, cygwinccompiler.py-shared.diff,
instead.

My reasons are the following:

1. support for older toolchains is retained
2. support for new toolchains (i.e., ld -shared) is added

The goal of my approach is to avoid breaking older toolchains while adding
better support for newer ones.