Include newline at end of GOTOOLCHAIN warning

[dagood]

I noticed that the GOTOOLCHAIN warning doesn't have a newline at the end, which is confusing in a shell because it looks like it isn't ready for the next command at first glance:

dagood@dagood-3:~/git/go$ GOTOOLCHAIN=auto msgo version
GOTOOLCHAIN is set to "auto" but only "local" is allowed.
To allow this, set MS_GOTOOLCHAIN_ALLOW_NON_LOCAL=1 in your environment.
Take into account that that could cause the go command to use a different toolchain than the Microsoft build of Go.dagood@dagood-3:~/git/go$

(Note the prompt appearing at the end of the last line rather than on a new one.)

New behavior:

dagood@dagood-3:~/git/go$ GOTOOLCHAIN=auto go/bin/go version
GOTOOLCHAIN is set to "auto" but only "local" is allowed.
To allow this, set MS_GOTOOLCHAIN_ALLOW_NON_LOCAL=1 in your environment.
Take into account that that could cause the go command to use a different toolchain than the Microsoft build of Go.
dagood@dagood-3:~/git/go$