buildx/bake/hclparser
Justin Chadwell 691723f9f9 bake: add timestamp function
Terraform includes a timestamp function to get the current time. go-cty
has imported a number of the timestamp functions to it's standard
library, however, this was one was not included.

This patch simply pulls in the TimestampFunc from Terraform's
internal/lang/funcs/datetime.go to allow easily fetching the current
time in bake.

Signed-off-by: Justin Chadwell <me@jedevc.com>
..
expr.go bake: new hclparser package
hclparser.go bake: forbid empty result and params in userfuncs
stdlib.go bake: add timestamp function