Turn on ninja errors for duplicate rules

Change-Id: Iadac88f8835121a8685bff835acba638100bb654
diff --git a/soong.bash b/soong.bash
index d88ebbf..f695e62 100755
--- a/soong.bash
+++ b/soong.bash
@@ -40,4 +40,4 @@
     fi
 fi
 
-"prebuilts/ninja/${PREBUILTOS}/ninja" -f "${BUILDDIR}/build.ninja" "$@"
+"prebuilts/ninja/${PREBUILTOS}/ninja" -f "${BUILDDIR}/build.ninja" -w dupbuild=err "$@"