build: increase macOS minimum supported version

Starting with V8 6.8, it will not be possible to build with macOS 10.10
and below. Those versions are already EoL.

PR-URL: #21883
Refs: nodejs/build#1358
Reviewed-By: Matheus Marchini <matheus@sthima.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jon Moss <me@jonathanmoss.me>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>

BUILDING.md

@@ -41,14 +41,13 @@ platforms in production.
 |--------------|--------------|----------------------------------|----------------------|------------------|
 | GNU/Linux    | Tier 1       | kernel >= 2.6.32, glibc >= 2.12  | x64, arm             |                  |
 | GNU/Linux    | Tier 1       | kernel >= 3.10, glibc >= 2.17    | arm64                |                  |
-| macOS/OS X   | Tier 1       | >= 10.10                         | x64                  |                  |
+| macOS/OS X   | Tier 1       | >= 10.11                         | x64                  |                  |
 | Windows      | Tier 1       | >= Windows 7/2008 R2/2012 R2     | x86, x64             | vs2017           |
 | SmartOS      | Tier 2       | >= 15 < 16.4                     | x86, x64             | see note1        |
 | FreeBSD      | Tier 2       | >= 10                            | x64                  |                  |
 | GNU/Linux    | Tier 2       | kernel >= 3.13.0, glibc >= 2.19  | ppc64le >=power8     |                  |
 | AIX          | Tier 2       | >= 7.1 TL04                      | ppc64be >=power7     |                  |
 | GNU/Linux    | Tier 2       | kernel >= 3.10, glibc >= 2.17    | s390x                |                  |
-| OS X         | Experimental | >= 10.8 < 10.10                  | x64                  | no test coverage |
 | GNU/Linux    | Experimental | kernel >= 2.6.32, glibc >= 2.12  | x86                  | limited CI       |
 | Linux (musl) | Experimental | musl >= 1.0                      | x64                  |                  |