doc: update minimum supported FreeBSD to 12.2

FreeBSD 11 goes out of support on 2021-09-30.
FreeBSD 12.1 is not supported since 2021-01-31.

PR-URL: #40179
Refs: https://en.wikipedia.org/wiki/FreeBSD_version_history#Version_history
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Michael Dawson <midawson@redhat.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: targos

BUILDING.md

@@ -113,11 +113,11 @@ platforms. This is true regardless of entries in the table below.
 | Windows          | x86 (native)     | >= Windows 8.1/2012 R2          | Tier 1 (running) / Experimental (compiling) <sup>[6](#fn6)</sup> | |
 | Windows          | x64, x86         | Windows Server 2012 (not R2)    | Experimental |                                   |
 | Windows          | arm64            | >= Windows 10                   | Tier 2 (compiling) / Experimental (running) |    |
-| macOS            | x64              | >= 10.13                        | Tier 1       | For notes about compilation see <sup>[8](#fn8)</sup>              |
+| macOS            | x64              | >= 10.13                        | Tier 1       | For notes about compilation see <sup>[7](#fn7)</sup>              |
 | macOS            | arm64            | >= 11                           | Tier 1       |                                   |
 | SmartOS          | x64              | >= 18                           | Tier 2       |                                   |
 | AIX              | ppc64be >=power7 | >= 7.2 TL04                     | Tier 2       |                                   |
-| FreeBSD          | x64              | >= 11                           | Experimental | Downgraded as of Node.js 12  <sup>[7](#fn7)</sup>     |
+| FreeBSD          | x64              | >= 12.2                         | Experimental |                                   |
 
 <em id="fn1">1</em>: GCC 8 is not provided on the base platform. Users will
 need the
@@ -151,11 +151,7 @@ are provided. However, tests in our infrastructure only run on WoW64.
 Furthermore, compiling on x86 Windows is Experimental and
 may not be possible.
 
-<em id="fn7">7</em>: The default FreeBSD 12.0 compiler is Clang 6.0.1, but
-FreeBSD 12.1 upgrades to 8.0.1. Other Clang/LLVM versions are available
-via the system's package manager, including Clang 9.0.
-
-<em id="fn8">8</em>: Our macOS x64 Binaries are compiled with 10.13 as a target.
+<em id="fn7">7</em>: Our macOS x64 Binaries are compiled with 10.13 as a target.
 However there is no guarantee compiling on 10.13 will work as Xcode11 is
 required to compile.