[ppc64le] Refer to the correct path for including ppc_vsx-inl.h in highway pkg

[mdafsanhossain]

Commit Message: Patch to refer to the correct path for including ppc_vsx-inl.h while building highway.
Additional Description: This fixes the following error which happens when compiler looks for the file in /usr/include while building highway as an external dependency.

ERROR: /home/user/.cache/bazel/_bazel_user/43a771d06a0b358af5ad67b4e5bcbc9d/external/highway/BUILD:156:11: Compiling hwy/targets.cc [for tool] failed: (Exit 1): gcc failed: error executing CppCompile command (from target @@highway//:hwy) /usr/bin/gcc -U_FORTIFY_SOURCE -fstack-protector -Wall -Wunused-but-set-parameter -Wno-free-nonheap-object -fno-omit-frame-pointer -g0 -O2 '-D_FORTIFY_SOURCE=1' -DNDEBUG -ffunction-sections ... (remaining 28 arguments skipped)

Use --sandbox_debug to see verbose messages from the sandbox and retain the sandbox build root for debugging
In file included from external/highway/hwy/targets.cc:23:
external/highway/hwy/highway.h:586:10: fatal error: hwy/ops/ppc_vsx-inl.h: No such file or directory
  586 | #include "hwy/ops/ppc_vsx-inl.h"
      |          ^~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.
Target //source/exe:envoy-static failed to build

Testing: Checked locally.
Docs Changes: No.

[mdafsanhossain]

@tedjpoole @jwendell Can you take a look at this one too?

[jwendell]

Could you please submit this change to envoy upstream first? Then the repos will sync after it lands there.

[jwendell]

closing, as it was submitted upstream.