ci : disable ccache for android

[CISC]

Due to impending updated eviction policy we need to trim down our Actions Cache. One of the largest offenders is the android build ccache which claim 400MB on every build and never has any cache hits, so effectively useless:

https://github.com/ggml-org/llama.cpp/actions/runs/18123052287/job/51571820863
https://github.com/ggml-org/llama.cpp/actions/runs/18092686960/job/51477080980

[CISC]

The docker publishing is the single largest offender with its buildkit blobs, way exceeding our 10GB limit already, I've tested changing the cache mode from max to min, but it makes no difference, we might have to disable GHA caching altogether for it... @ngxson @ggerganov

[slaren]

The docker images are only built once per day overnight, so it should be ok if they need more time.

[CISC]

The docker images are only built once per day overnight, so it should be ok if they need more time.

I'm not sure why, but the CUDA Light image has been building for hours now in my test (while the Full image only took 45 minutes).

[CISC]

The docker images are only built once per day overnight, so it should be ok if they need more time.

I'm not sure why, but the CUDA Light image has been building for hours now in my test (while the Full image only took 45 minutes).

Tried switching to local cache, but then the CUDA image fails with System.IO.IOException: No space left on device, which I guess is unsurprising as it's 4GB++ of layer caches...