Makefile: fix arguments to go, not matching what go expects

This caused gcc to receive the actual argument "''" or for example
"'-Wl,-O1,--sort-common,--as-needed,-z,relro,-z,now'" and then error
with
gcc: error: '-Wl,-O1,--sort-common,--as-needed,-z,relro,-z,now': No such file or directory

Furthermore, the trimpath arguments tried to trim an actual path
resembling "'$PWD'", which did nothing as the literal single quotes were
not valid in this context.

Both issues can be fixed by assigning arguments to the go compiler using
the argv notation { "-flag", "argument" } rather than { "-flag=argument" }.

[ci skip]

[ci skip]

Allows sending `api.github.com` OAuth token to all `*.github.com`
subdomains. In case `git.my.org` is an Enterprise instance, this allows
sending the token to `git.my.org` and all of `*.git.my.org`.

https://travis-ci.org/github/hub/jobs/484769927

[ci skip]

New `hub api` command for making GitHub API requests

- sort query string in cache key
- include "Accept", "Authorization" headers in cache key
- allow caching of `/graphql` responses

This ensures that calling `hub api http://example.com/foo` doesn't
accidentally send the OAuth token for `github.com` to `example.com`.

- print error output on stderr instead of stdout
- only prompt to open an issue if connected to terminal
- get rid of "always" option in the prompt
- empty response to the prompt is interpreted as a "no"

[ci skip]

Fixes #2011 [ci skip]

[ci skip]

Go 1.8 doesn't have the `testing.Helper()` method
https://travis-ci.org/github/hub/jobs/481181084