Changes

ci.inria.fr/msvc: assume MSBuild is in the PATH envvar

Should be set in ciprofile.bat

And don't enforce the PlatformToolset either,
since that v110 is not available in all VS installtion.

Signed-off-by: Brice Goglin <Brice.Goglin@inria.fr>
(cherry picked from commit 448af6ff7904e4b84d175d2c5c33e12c0ef7a40e)