add gvm use -n/--no-install option

[graphaelli]

Mostly to enable gvm use tip -n.

[15:02:09] ~/src/gvm (use-no-install) $ cat ~/.gvm/cache/go.meta 
{"Updated":"2021-01-07T14:23:47.883139-05:00"}

[15:02:15] ~/src/gvm (use-no-install) $ gvm use tip -n
export GOROOT="/Users/gil/.gvm/versions/gotip.darwin.amd64"
export PATH="/Users/gil/.gvm/versions/gotip.darwin.amd64/bin:$PATH"

[15:02:18] ~/src/gvm (use-no-install) $ cat ~/.gvm/cache/go.meta 
{"Updated":"2021-01-07T14:23:47.883139-05:00"}

[15:02:19] ~/src/gvm (use-no-install) $ gvm use tip
export GOROOT="/Users/gil/.gvm/versions/gotip.darwin.amd64"
export PATH="/Users/gil/.gvm/versions/gotip.darwin.amd64/bin:$PATH"

[15:03:11] ~/src/gvm (use-no-install) $ cat ~/.gvm/cache/go.meta 
{"Updated":"2021-01-08T15:02:23.408087-05:00"}

[andrewkroh]

Hi Gil, so is this to enable the use of gvm use tip without having it do an update?

[graphaelli]

Yes, exactly

[andrewkroh]

LGTM

[andrewkroh]

I'll add a changelog entry and make a release.