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

build/fbcode_builder/getdeps/load.py

@@ -271,6 +271,7 @@ class ManifestLoader(object):
         env = {}
         env["install_dir"] = self.build_opts.install_dir
         env["scratch_dir"] = self.build_opts.scratch_dir
+        env["vcvars_path"] = self.build_opts.vcvars_path
         env["os"] = self.build_opts.host_type.ostype
         env["distro"] = self.build_opts.host_type.distro
         env["distro_vers"] = self.build_opts.host_type.distrovers