I think install msys using mingw-get
then install tdm “somewhere”
then
edit msys\1.0\etc\fstab
to look like
G:\installs\tdm-46-sljl\ /mingw
And you’re good to go.
That didn’t work. (seems to lose access to autoconf, etc.) Latest thought is to install msys/mingw using mingw-get, then just add your tdm bin folder first in your path (msys.bat maybe, at the top?)
Maybe you can edit fstab and add a new mount point
G:\installs\tdm_installs /mingw-tdm