Windows JNI: make the builder .bat executable 

Came up while working on https://github.com/bazelbuild/bazel/issues/2725

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Change-Id: I923690642d0fc93dcdb5050837b5ddaaa2a1d494
Reviewed-on: https://cr.bazel.build/9469
PiperOrigin-RevId: 150880961
MOS_MIGRATED_REVID=150880961
diff --git a/src/main/native/build_windows_jni.sh b/src/main/native/build_windows_jni.sh
index 97f37e9..a662678 100755
--- a/src/main/native/build_windows_jni.sh
+++ b/src/main/native/build_windows_jni.sh
@@ -96,4 +96,5 @@
 EOF
 
 # Invoke the file and hopefully generate the .DLL .
+chmod +x "${VSTEMP}/windows_jni.bat"
 exec "${VSTEMP}/windows_jni.bat"