MSVC x86 build fails because mingw's x86 gendef creates malformed .def files

In some cases w32 (x86) mingw gendef misdetects the calling convention of functions and exports them with a @0 or @4, etc, appended to the end. In cases where the calling convention is stdcall or cdecl ending in @N it duplicates them.

This leads to these libraries being unusable from MSVC since we use the generated .def to create .lib import libraries using MSVC's lib.exe. Trying to link to them causes linker errors about unresolved symbols. At least the following libraries are affected: libopenjpeg, libssl, libspandsp, maybe more.

Due to this issue, the MSVC build fails on Windows x86 while linking gst-plugins-bad-1.0.

Upstream bug: https://sourceforge.net/p/mingw-w64/bugs/299/ (no activity in the last 7 years)