getdeps: hash over the visual studio path
getdeps: hash over the visual studio path

Summary:
I was testing vs2019 vs vs2017 and realized that
we weren't reconfiguring when the toolchain was changed;
this resolves that.

Reviewed By: genevievehelsel

Differential Revision: D20795118

fbshipit-source-id: db80f090367cacfcc6b53887b77cf949f9cef0e6

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