Brew build on ubuntu fails when environment variable CC is set

[jkamins7]

Steps to reproduce:

export CC=clang

Then follow the tutorial

# Install bazelisk using Homebrew.
$ brew install bazelisk

# Install Clang/LLVM using Homebrew.
# Many Clang/LLVM releases aren't built with options we rely on.
$ brew install llvm
$ export PATH="$(brew --prefix llvm)/bin:${PATH}"

# Download Carbon's code.
$ git clone https://github.com/carbon-language/carbon-lang
[error.log](https://github.com/carbon-language/carbon-lang/files/9184539/error.log)

$ cd carbon-lang

# Build and run the explorer.
$ bazel run //explorer -- ./explorer/testdata/print/format_only.carbon

Output error.log

It seems like this issue is in this part of the code:

https://github.com/carbon-language/carbon-lang/blob/25b6a36b0d323fc81f0afe149552b5b0f6fc1350/bazel/cc_toolchains/clang_configuration.bzl#L29-L33

[jonmeow]

Can you provide the following:

echo $CC
$CC --version

[jkamins7]

This would not have been the original output, since I installed homebrew after my first attempt. However, I'm still able to replicate the error

> echo $CC
clang

> $CC --version
Homebrew clang version 14.0.6
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/linuxbrew/.linuxbrew/opt/llvm/bin

Also, it's definitely CC since the following works

unset CC
bazel run //explorer -- ./explorer/testdata/print/format_only.carbon

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[jonmeow]

I think this was addressed by #1724