Yay I'm on the interwebz!
I've glanced over the extremely detailed instructions (kudos for that) and noticed conceptual errors around mingw32-make:
- this is not a compiler
- the bitness of the mingw32-make executable does not at all influence what the actual compiler does.
- a 64-bit program will never attempt to load a 32-bit DLL. It will skip it instead. The error you are showing (0xc000007b) signifies failure to find a loadable DLL. Say for example both are in PATH:
in this case, when loading a 64-bit application linked to the libiconv DLL, the Windows loader will find the 32-bit DLL file in the first directory, skip it cause it's 32-bit, and continue with the next PATH entry, where it finds a usable DLL and loads that. Your setup to install everything to /local/ will not prevent 32 and 64-bit library files to overwrite each other if you build both.
In the Qt part, you say the option -static-libstdc++ will fail, but this is only true for TDM's toolchain. If you want to increase the speed of the build, perhaps consider not building Qt from MSYS, and using Qt's jom to parallellize command execution.