Fixes "cd" on Windows when build and repo directory are on different drive (#77)

Fixes https://github.com/theoremlp/rules_multitool/issues/52

multitool/private/run_in.template.bat

diff --git a/multitool/private/run_in.template.bat b/multitool/private/run_in.template.bat
index 0a2a83a..d8935a5 100644
--- a/multitool/private/run_in.template.bat
+++ b/multitool/private/run_in.template.bat
@@ -1,3 +1,3 @@
 @set tool=%cd%\{{tool}}
-@cd %{{env_var}}%
+@cd /D %{{env_var}}%
 @%tool% %*