``get_version_bcd()`` shouldn't raise exception for non-semantic version tag.

Hi,

I've been trying to build the ORBTrace bitfile on a branch that doesn't use semantic versioning. What do you think about updating get_version_bcd() to just print a warning and return 0 when it doesn't see a tag of the correct format? Or is there some other way you can think of to handle this case?

[zyp]

The reason it's currently an exception is so that e.g. CI doesn't silently create a build with the wrong bcdDevice value if tags haven't been fetched properly, ref. 7d5d341.

If you're building a modified branch, the intention is for it to look up the most recent tagged ancestor and derive from that, and since the commit adding get_version_bcd() has a tagged ancestor, this should always be possible unless you're adding your own tags on your branch.

I'm open to adding a builder argument that overrides bcdDevice and thereby omits the call to get_version_bcd().

[Hoernchen]

The easiest way to break this is not to modify anything: just do a shallow clone because you don't plan to modify anything and it breaks...