chore(ci): fix failure in detecting compilers in clang-tidy job

[amoeba]

The clang-tidy job recently started failing.

Last success: https://github.com/apache/arrow-adbc/actions/runs/30502165159/job/90743952843
First failure: https://github.com/apache/arrow-adbc/actions/runs/30596999777/job/91051511466

The error is,

Could not find the compiler specified in the environment variable CC: /home/runner/work/arrow-adbc/arrow-adbc/build/tidy/x86_64-conda-linux-gnu-cc.

Note that path to x86_64-conda-linux-gnu-cc is relative to the CWD which is wrong.

The difference seems to be:

In a successful run, I see:

++ readlink -f /home/runner/miniconda3/envs/test/bin/x86_64-conda-linux-gnu-cc
++ readlink -f /home/runner/miniconda3/envs/test/bin/x86_64-conda-linux-gnu-c++

In a failed run, I see:

++ readlink -f x86_64-conda-linux-gnu-cc
++ readlink -f x86_64-conda-linux-gnu-c++

A notable difference between these two environments is that the last working build used gcc_linux-64=14.3.0 whereas the failures started after gcc_linux-64=14.4.0 showed up.

[amoeba]

Seems plausible it was caused by https://github.com/conda-forge/ctng-compiler-activation-feedstock/blob/main/recipe/build_scripts.sh#L222-L224 which looks like it just came out.

I can reproduce what see in CI with:

$ conda create -n test-old gcc_linux-64=14.3.0 -c conda-forge
$ conda activate test-old
$ echo $CC
/opt/conda/envs/test-old/bin/x86_64-conda-linux-gnu-cc

$ conda create -n test-new gcc_linux-64=14.4.0 -c conda-forge
$ conda activate test-new
$ echo $CC
x86_64-conda-linux-gnu-cc