fix windows builds

Summary:
The new boost has an MSVC detection algorithm that 1) I don't
understand and 2) does not even seem deterministic. Since our internal
builds are pinned to vc142, force that in the manifest.

Reviewed By: fanzeyi

Differential Revision: D34085081

fbshipit-source-id: d8ce4d8e28aad14f6fa60f9227dafb546ce321e5

build/fbcode_builder/getdeps/builder.py

@@ -486,6 +486,14 @@ if __name__ == "__main__":
         self.defines = defines or {}
         if extra_cmake_defines:
             self.defines.update(extra_cmake_defines)
+
+        try:
+            from .facebook.vcvarsall import extra_vc_cmake_defines
+        except ImportError:
+            pass
+        else:
+            self.defines.update(extra_vc_cmake_defines)
+
         self.loader = loader
         if build_opts.shared_libs:
             self.defines["BUILD_SHARED_LIBS"] = "ON"