build progress counter is no longer visible

[bergmark]

I noticed this after upgrading to 1.0.2, the progress counter never shows when building multiple packages, instead there's just an empty line. If i hit Ctrl-C the progress prints before stack exits

test-1: build
^CProgress: 0/37user interrupt
Progress: 1/37⏎

[mgsloan]

Hmm, good point! Regression caused by 3003354 , should have tested that more thoroughly. The fix is to flush stderr after writing the sticky message.