This fixes the following failure when doing a clean build (in particular
no .ninja* lying around) of lib/libMLIRLinalgToStandard.a only:
```
In file included from mlir/include/mlir/Dialect/Vector/Transforms/VectorTransforms.h:12,
from mlir/include/mlir/Dialect/Linalg/Transforms/Transforms.h:21,
from mlir/lib/Conversion/LinalgToStandard/LinalgToStandard.cpp:15:
mlir/include/mlir/Dialect/Vector/Transforms/VectorRewritePatterns.h:20:10: fatal error: mlir/Dialect/Vector/Transforms/VectorTransformsEnums.h.inc: No such file or directory
```