New macOS Build

Hi Fahar,

I've stood up a new macOS build server (as the old one is getting
unreliable). Can you please test the build at
https://developer.pgadmin.org/builds/2019-04-15-macos2-test2/? Please
remember to test the file dialogue and external processes as those are the
places most likely to be affected (everything else is likely to be fine if
we can connect to the database, browse the schema and run queries).

All;

It seems that supporting macOS < 10.12 (Sierra) is somewhat hard now, as Qt
have dropped support for it, and Apple also seem to be using that as a
compatibility break version. Does anyone see any major reason why we can't
require 10.12 or later for pgAdmin?

Note that I've already updated the website to say we only support 10.12+.
For now though, that's just meant as "discouragement" rather than a hard
and fast rule.

Thanks.

--
Dave Page
Blog: http://pgsnake.blogspot.com
Twitter: @pgsnake

EnterpriseDB UK: http://www.enterprisedb.com
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