@PDN_GMIC said that he has to rewrite instruction due to new gmic changes via gmic-sharp-native@github. Probably not my fault, but we’ll see.
That is the problem.
@Reptorian built libgmic.a in ../gmic/src and the build command is looking in for it in ../gmic/gcc64.
The -L../gmic/gcc64 command must be changed to -L../gmic/src for libgmic.a to be found.
The -L../gmic/gcc64 in my example assumed that libgmic.a was built using the CMake files, and those files are broken on MinGW.
CMake generates MinGW makefiles that contain an invalid command (-D-Wl), and it appears that there is no way to override cimg_display for Windows.
The reason my instructions build libgmic.a and link to it is so that I can build a statically linked DLL on Windows.
Including gmic.cpp when compiling the gmic-sharp-native library causes a linker error when statically linking to libcurl.a, for some reason it works when linking to libgmic.a and libcurl.a.