[llvm] [ci] Use different emoji for Linux and Windows job titles on GitHub (PR #142101)

[David Spickett via llvm-commits]

DavidSpickett wrote:

Looks like the metrics might cope with a pipeline name change - https://github.com/llvm/llvm-project/blob/37edd2c1c32bf7599af28b96ae5adf909e96fc58/.ci/metrics/metrics.py#L58, but no point taking the risk just for some emoji.

Example build where GitHub just prints `:linux:` https://github.com/llvm/llvm-project/actions/runs/15337076175.



https://github.com/llvm/llvm-project/pull/142101