Trying to build `libfsm` with a naked `pmake` hangs.

[John VanEnk]

I had expected pmake to produce something, but it hung. I applied strace to the build, and found that it was hanging on sed. After reading, I realized that the $PREFIX is needed to make progress. Is this expected? Could it be made to emit an error instead of hanging?

[moon-chilled]

pmake -r

[Katherine]

This happens when -r is absent because that brings in the stock sys.mk stuff. I added a guard in 8552cd7, which bails out with an error when sys.mk is present. Thanks for the idea!