Minor code improvement. Review comment by Eric V. Smith
Issue #19106: Touch generated files to be 1s newer than their youngest source.
Issue #19106: Add buildbottouch target.
Add a "skull and crossbones" to Py_AddPendingCall.
Issue #12641: Avoid passing "-mno-cygwin" to the mingw32 compiler, except when necessary.
Patch by Oscar Benjamin.