IRSL: Fix discovery of VS 2019 v141 toolset redistributables
This updates the logic in
InstallRequiredSystemLibraries so that the v141 redistributable path is searched for in multiple VS versions (VS2017 and VS2019).
A second minor commit fixes a typo that would prevent a warning message when the
MSVC_TOOLSET_VERSION is greater than or equal to 143.
Fixes: #19488 (closed)