Unfucked setenv.bat

Summary: setenv.bat.dist was a bit fucked, fixed it up

Test Plan:
copy setenv.bat.dist to setenv.bat and update ARC_HOME to point to your arcanist directory
run setenv.bat

Reviewers: #ss14_developers, Kraso

Reviewed By: #ss14_developers, Kraso

Subscribers: YotaXP

Differential Revision: http://phab.nexisonline.net/D29

setenv.bat.dist

@@ -1,3 +1,8 @@
+REM @echo off
 SET ARC_HOME=E:\dev\arcanist\arcanist
-call arc.bat > nul 2>&1
-if %ERRORLEVEL%==9009 SET PATH=%PATH%;%ARC_HOME%\bin
+CMD /C call arc.bat > nul 2>&1
+if ERRORLEVEL 1 GOTO path
+GOTO end
+:path
+SET PATH=%PATH%;%ARC_HOME%\bin
+:end