[CI] the r-devdocs build errors when brew installing gcc

[asfimport]

This affects github-test-r-devdocs (R devdocs macOS-latest). The brew step to install gcc fails, and then OpenBLAS fails as well.
See https://github.com/ursacomputing/crossbow/runs/2573031778#step:8:1494

Reporter: Mauricio 'Pachá' Vargas Sepúlveda / @pachadotdev
Assignee: Jonathan Keane / @jonkeane

PRs and other links:

• GitHub Pull Request #10328

_{Note: This issue was originally created as ARROW-12785. Please see the migration documentation for further details.}

[asfimport]

Jonathan Keane / @jonkeane:
I can't fully explain why, but something about Homebrew/homebrew-core#76984 is triggering gcc to be installed with brew (which fails to link because there's a macos version of gfortran in the way).

The last passing build does not include gcc at all:

==> Installing dependencies for apache-arrow: gflags, glog, abseil, protobuf, re2, grpc, openblas, numpy, rapidjson, snappy and thrift

But subsequent builds have:

==> Installing dependencies for apache-arrow: gflags, glog, abseil, protobuf, re2, grpc, gcc, openblas, numpy, rapidjson, snappy and thrift

For now I'm removing the offending gfortran from the path so that brew will happily install gcc regardless.

[asfimport]

Jonathan Keane / @jonkeane:
Issue resolved by pull request 10328
#10328