PR #13408: Fix mlir_hlo tests on Windows
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PR #13408: Fix mlir_hlo tests on Windows

Imported from GitHub PR https://github.com/openxla/xla/pull/13408

This PR aims to fix the mlir_hlo tests which are designed to test the implementation of the HLO (High-Level Optimizer) for MLIR (Multi-Level Intermediate Representation).

**Error**
mlir_hlo tests were failing on the Windows platform with an error shown below:

INFO: From Testing //xla/mlir_hlo/tests:Dialect/mhlo/verifier_while_op.mlir.test:

==================== Test output for //xla/mlir_hlo/tests:Dialect/mhlo/verifier_while_op.mlir.test:

lit.py: C:\Users\mraunak\AppData\Local\Temp\Bazel.runfiles_8ccro7s1\runfiles\llvm-project\llvm\utils\lit\lit\llvm\config.py:57: note: using lit tools: C:\Program Files\Git\usr\bin

lit.py: C:\Users\mraunak\AppData\Local\Temp\Bazel.runfiles_8ccro7s1\runfiles\llvm-project\llvm\utils\lit\lit\llvm\subst.py:133: **fatal**: **Did not find FileCheck in external/llvm-project/llvm**

**Solution**
Tweaked the PATH to correctly find the tools required for executing LIT tests on the Windows platform such as FileCheck.
Copybara import of the project:

--
b71b35ffac522acd8989d3ea79e038a4e30b7493 by Raunak <mayank.kumar.raunak@intel.com>:

Fix mlir_hlo tests on Windows

Merging this change closes #13408

FUTURE_COPYBARA_INTEGRATE_REVIEW=https://github.com/openxla/xla/pull/13408 from Intel-tensorflow:mraunak/mlir_xla b71b35ffac522acd8989d3ea79e038a4e30b7493
