Emacs crashing after M-x compile after Cygwin updates

[Bruce Mardle]

Hi, all.
I've been happily compiling simple C programs under Emacs (emacs-w32) under Cygwin. Yesterday I wanted to install libedit-dev. While I was doing that, setup...exe marked a few dozen other packages for upgrades. I didn't notice which. Now, if I `emacs hello.c` and M-x compile gcc -o hello hello.c the compilation works... but then, a few seconds later, Emacs SEGVs. emacs-nox does the same but without the delay.
I've tried Emacs versions 27.2-1, 28.0.60-1.f7e6c199bf, and 27.1. Then, in case it was gcc doing something naughty, I changed that from version 11.2.0 to 10.2.0-1. Same problem all the way. Running gcc from the terminal emulator works (but then I don't get to use Emacs' M-x ` and the like).
I'm using 64-bit Windows 7 Pro [blush]. Is it still supposed to work on that? I don't seem to have a problem with a laptop running Windows 10.
`uname -r` returns 3.3.4(0.341/5/3).
I've spent a few hours looking at the mailing list archives (probably incompetently) and Googling, without success.