The standard host triplet for mingw tools is is something like
x86_64-w64-mingw32 on debian and something like x86-64-w64-mingw32.shared for
mxe (http://mxe.cc). Detect windows packaging correctly for these build types.
case $host in
*-apple-darwin*) lyx_use_packaging=macosx ;;
*-pc-mingw*) lyx_use_packaging=windows ;;
+ *-mingw32*) lyx_use_packaging=windows ;;
*haiku*) lyx_use_packaging=haiku ;;
*) lyx_use_packaging=posix ;;
esac])