WarpIN wpi builder can attempt to use wrong wic.exe

[stevenhl]

As luck would have it, there is more than one program named wic.exe. OpenWatcom has an interface builder application named wic.exe. Bld_fm2_wpi.cmd will attempt to use this wic.exe if it happens to find it.

A reasonable solution is to check that the directory which contains wic.exe also contains warpin.exe and wpirtl.dll.

This should catch all but the worst failure modes.