grok: fix sonoma build and linux build

[chenrui333]

• [x] Have you followed the guidelines for contributing?
• [x] Have you ensured that your commits follow the commit style guide?
• [x] Have you checked that there aren't other open pull requests for the same formula update/change?
• [x] Have you built your formula locally with HOMEBREW_NO_INSTALL_FROM_API=1 brew install --build-from-source <formula>, where <formula> is the name of the formula you're submitting?
• [x] Is your test running fine brew test <formula>, where <formula> is the name of the formula you're submitting?
• [x] Does your build pass brew audit --strict <formula> (after doing HOMEBREW_NO_INSTALL_FROM_API=1 brew install --build-from-source <formula>)? If this is a new formula, does it pass brew audit --new <formula>?

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[chenrui333]

  gcc-11 -c -pipe -fPIC -I. -O2 -I/usr/local/include -DPLATFORM_GNULinux  grok.c -o grok.o
  In file included from grok_capture.h:4,
                   from grok.h:136,
                   from grok.c:1:
  grok_capture_xdr.h:9:10: fatal error: rpc/rpc.h: No such file or directory
      9 | #include <rpc/rpc.h>
        |          ^~~~~~~~~~~
  compilation terminated.

[github-actions[bot]]

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