Replaced non-existent argument 'target_arch' for 'vs_target_arch'.

git-svn-id: https://llvm.org/svn/llvm-project/zorg/trunk@371690 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/buildbot/osuosl/master/config/builders.py b/buildbot/osuosl/master/config/builders.py
index aa209b4..2544658 100644
--- a/buildbot/osuosl/master/config/builders.py
+++ b/buildbot/osuosl/master/config/builders.py
@@ -731,7 +731,7 @@
                         clean=False,
                         checkout_lld=False,
                         vs="autodetect",
-                        target_arch='x64',
+                        vs_target_arch='x64',
                         testStage1=True,
                         useTwoStage=True,
                         stage1_config='Release',