[pull] master from flutter:master - #3

…n `main` when up to date (#172141)

The `frameworkVersion` string written to the version files wasn't
actually parsable by `GitTagVersion` as it didn't match the format
output by `git`.

This change updates the `frameworkVersion` format to use a `-` instead
of a `.` before the commit count and adds support to the version parsing
regex to handle both `.` and `-` separators before the commit count.

Fixes #172091