feat: bump to llvm-20 and rust 1.87

[daniel-noland]

This is our (roughly) twice per year LLVM bump. Rejoice :)

[qmonnet]

2025-05-16T11:28:42.7130786Z valkey> 
2025-05-16T11:28:42.7130943Z valkey> !!! WARNING The following tests failed:
2025-05-16T11:28:42.7131089Z valkey> 
2025-05-16T11:28:42.7131324Z valkey> *** [err]: CLUSTER SLOT-STATS cpu-usec for blocking commands, unblocked on timeout. in tests/unit/cluster/slot-stats.tcl
2025-05-16T11:28:42.7131600Z valkey> Timeout waiting for blocked clients
2025-05-16T11:28:42.8079356Z valkey> Cleanup: may take some time... OK
2025-05-16T11:28:42.8505443Z note: keeping build directory '/home/runner/_work/_temp/nix-build-valkey-8.0.2.drv-0/build'
2025-05-16T11:28:42.8505854Z error: builder for '/nix/store/iras3vv5013knqnsr1fa9clzlqg69xfz-valkey-8.0.2.drv' failed with exit code 1
2025-05-16T11:28:42.8553197Z error: 1 dependencies of derivation '/nix/store/rhpywjhbplx91wc11apdcby8p7zl5dm5-redis-test-hook.drv' failed to build
2025-05-16T11:28:42.8554003Z error: 1 dependencies of derivation '/nix/store/icxzc87v0g08sazq3n90qy5b23sy4z1k-python3.12-mocket-3.13.4.drv' failed to build
2025-05-16T11:28:42.9041536Z building '/nix/store/gcy1rbx9q4vgryll3nykix884k7v8wn0-qtbase-6.9.0-only-plugins-qml.drv'...
2025-05-16T11:28:42.9046778Z error: 1 dependencies of derivation '/nix/store/g4d27s2a2zfklnp37dh6k76p8ymkcfv4-python3.12-geoip2-5.0.1.drv' failed to build
2025-05-16T11:28:42.9049994Z error: 1 dependencies of derivation '/nix/store/85c0jhalaxfkgaz6f2zk4dsk3wj4zd1z-python3.12-django-4.2.20.drv' failed to build
2025-05-16T11:28:42.9055551Z error: 1 dependencies of derivation '/nix/store/a0g0c55033wn6wga3if9w3zil1c7w8qf-python3.12-pytest-django-4.10.0.drv' failed to build
2025-05-16T11:28:42.9057125Z error: 1 dependencies of derivation '/nix/store/d83a0vpicl02k99wfa6szg9yym9j7apw-python3.12-diskcache-5.6.3.drv' failed to build
2025-05-16T11:28:42.9058565Z error: 1 dependencies of derivation '/nix/store/hl3qyssd0avfmzhzvm4rqn34fcvngirr-python3.12-fasteners-0.19.drv' failed to build
2025-05-16T11:28:42.9059968Z error: 1 dependencies of derivation '/nix/store/v3fr0z3339yxflx1a2iwnscbidgv90ny-python3.12-zarr-2.18.7.drv' failed to build
2025-05-16T11:28:42.9061631Z error: 1 dependencies of derivation '/nix/store/j0qjw862nn8abazbmba1v6d6q8k8nhxd-python3.12-tifffile-2025.3.30.drv' failed to build
2025-05-16T11:28:42.9080151Z note: keeping build directory '/home/runner/_work/_temp/nix-build-qtbase-6.9.0-only-plugins-qml.drv-0/build'
2025-05-16T11:28:42.9267773Z error: 1 dependencies of derivation '/nix/store/xfba1503imw30f85ymjxlcgsd6bnh2lj-python3.12-scikit-image-0.25.2.drv' failed to build
2025-05-16T11:28:42.9268272Z error: 1 dependencies of derivation '/nix/store/2dk6vzpl4lpdrbwmr1ai53k1jhim8r6s-python3.12-plotly-5.24.1.drv' failed to build
2025-05-16T11:28:42.9268719Z error: 1 dependencies of derivation '/nix/store/9c51y30lyqjsb8ymin50x0kisa50y6i9-python3.12-igraph-0.11.8.drv' failed to build
2025-05-16T11:28:42.9269170Z error: 1 dependencies of derivation '/nix/store/kzxd4wa596s0vjjf195nav5508z5ih72-flatten-references-graph-0.1.0.drv' failed to build
2025-05-16T11:28:42.9269605Z error: 1 dependencies of derivation '/nix/store/1drnjb6p329jsyysjihdjamwlnail95q-docker-layers.drv' failed to build
2025-05-16T11:28:42.9270022Z error: 1 dependencies of derivation '/nix/store/p05rqi5qlizm3avh0smcwxkkh8kw1p5j-libc-env-conf.json.drv' failed to build
2025-05-16T11:28:42.9270467Z error: 1 dependencies of derivation '/nix/store/xmg9hwpmvpm5bszi3cvigdx9fs7bpfib-stream-libc-env.drv' failed to build
2025-05-16T11:28:43.0175412Z error: 1 dependencies of derivation '/nix/store/vydyvw0wirawadjnnw3ccgia8vr8jqdx-libc-env.tar.gz.drv' failed to build
2025-05-16T11:28:43.1041634Z error: Recipe `_nix_build` failed with exit code 1
2025-05-16T11:28:43.1055563Z ##[error]Process completed with exit code 1.

Let's try building again

[qmonnet]

@daniel-noland do you have any idea of what component's failing here?

[daniel-noland]

I spent some time looking into this yesterday but it is a bit of a maze