OK, I was able to run what appears to be the 32-bit test via the following command line, launched from the 32-bit build target directory:
./wine programs/winetest/i386-windows/winetest.exe -o - cmd.exe
Here is the only output I see related to the file that I changed, directory.c:
md.exe:directory start programs/cmd/tests/directory.c 06c0:directory: 24 tests executed (0 marked as todo, 0 as flaky, 0 failures), 0 skipped. cmd.exe:directory:06c0 done (0) in 0s 90B