[Bug go/63731] Fallback to netgo does not work

["ian at airs dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63731

--- Comment #36 from Ian Lance Taylor <ian at airs dot com> ---
Lynn added a new facility.  Some notes on docs:

As far as documentation, I tried to find some documentation on build tags in
general and netgo specifically because it seems like this should be documented
there, but did not find much.  Here are some ideas:
- add something to the 'go help build' output about the use of the netgo tag in
general and how it would be used to work around the static linking 
warning/problem against libnss and the workarounds for gc and gccgo
- if there is something somewhere else that describes the netgo tag and when to
use it, then add something about how to achieve the same effect in gccgo
- seems like it would be good to have documentation describing the differences
in using gccgo vs. gc and this would be included in that, however that is a
bigger work item and would require more thought on what to include in such a
document.