Build : Set MSVC_VERSION

SCons will use the latest installed MSVC version by default. We are
currently using MSVC 2019 (or for this purpose, toolset 14.2, see
https://devblogs.microsoft.com/oldnewthing/20221219-00/?p=107601 for a
valiant attempt at explaining MSVC version numbering) so building with
a newer compiler installed will fail with "unexpected compiler version"
errors. This mismatch will go away when we update to MSVC 2022, but will
almost certainly come up again, so it's worth codifying the version we
use.

Author: ericmehl

SConstruct

@@ -967,6 +967,7 @@ o.Add(
 ###########################################################################################
 
 env = Environment(
+	MSVC_VERSION = "14.2",
 	options = o
 )