Add a third bootstrap stage with Go1.21.x necessary for go1.22 bootstrap.
go-bootstrap-stage1 is Go1.4.x, the final version to support bootstrap using a C
compiler (later versions require the Go compiler for bootstrapping).
See: https://go.dev/doc/install/source#bootstrapFromSource
go-bootstrap-stage2 is Go 1.19.13, the last version to support bootstrap using
the Go1.4.x compiler.
go-bootstrap-stage3 is Go 1.21.8, the last version to support bootstrap using
the Go1.19.13 compiler. Go 1.20 requires a minimum of go 1.17.13 to bootstrap.
See: https://go.dev/doc/go1.20#bootstrap
This patch is in preparation for bumping the host-go package to >go1.22.x, which
requires a minimum of Go1.20.x for bootstrap.
See: https://go.dev/doc/go1.22#bootstrap
Signed-off-by: Christian Stewart <christian@aperture.us>
[Arnout: add GOCACHE definition]
Signed-off-by: Arnout Vandecappelle <arnout@mind.be>
f00eb37de9