Consider adding `-tags timetzdata` to Go builds by default.

[jmalloc]

See https://pkg.go.dev/time/tzdata

Doing so removes Go's reliance on the system timezone database. I am in favour of this for two main reasons:

• Removes the need to bake this timezone data into docker images (allowing for Go builds directly from scratch)
• Potentially improves build repeatability, as the database moves in lockstep with the Go version

It does have a 450KB size penalty, which is considerable, so it should definitely be possible to turn this off with a makefile variable.

Alternatively, if there were some way we could force Go to avoid the system database such that you have to explicitly turn this option on to use any timezone data, that could also work.