fix(cmd/build): populate date variable when not set through ldflags (#11316)

# Which Problems Are Solved

When building zitadel through `go build` or using an IDE debugging tool,
ldflags are not passed by dedault. In the past this was taken care of by
the `make compile` command, which got replaced by NX. The `nx
@zitadel/api:build` command does not set the ldflags either. Only the
`pack-platform` command does.

Because the ldflags aren't passed, the `date` and other variables remain
empty in the `cmd/build` package. During init of the package, if the
`version` is empty it defaults to the `date` variable. When the `date`
field was empty, the parsed `dateTime` would default to `time.Now()`,
but the `date` variable remained empty, resulting in a empty version.

A consistently empty version string prevents upgrades of projections on
dev systems, as the version from the last run is used.

# How the Problems Are Solved

If date failed to parse and `dateTime` is set to Now, use the formated
string of `dateTime` as `date`.

# Additional Context

- Blocks https://github.com/zitadel/zitadel/pull/11239

cmd/build/info.go

@@ -23,6 +23,7 @@ func init() {
 	if err != nil {
 		logging.WithError(err).Warn("could not parse build date, using current time instead")
 		dateTime = time.Now()
+		date = dateTime.Format(time.RFC3339)
 	}
 	if version == "" {
 		logging.Warn("no build version set, using timestamp as version")