CI: Missing ARM cross-toolchain

[aperezdc]

The CI has been having failures lately and the reason is that the toolchain installer seems to be gone:

% curl -LI https://people.igalia.com/psaavedra/toolchains/browsers-glibc-x86_64-core-image-weston-browsers-cortexa9t2hf-neon-wandboard-mesa-toolchain-1.0.sh 
HTTP/2 404 
server: nginx/1.22.1
date: Wed, 29 Apr 2026 07:34:39 GMT
content-type: text/html; charset=iso-8859-1

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