Github Actions: mismatch with work/ dir causes V8 to never be cached

[hishamhm]

util/runtimes/v8.sh manages the caching of its assets, aiming to take advantage of the "Setup cache - work/ dir" step performed by the Github Actions ci.yml workflow.

However, there seems to be a confusion regarding the work directory: there are currently two work/ directories: one at the root of the runner's $HOME directory, and another one inside the repo checkout used by the runner.

v8.sh was being launched with the former by the wasm-runtime action and using the latter for caching via DIR_DOWNLOAD, resulting in a situation like this:

caching built assets in /home/runner/work/ngx_wasm_module/ngx_wasm_module/work/downloads/v8-10.5.18...
'/home/runner/work/v8-10.5.18/include/wasm.h' -> '/home/runner/work/ngx_wasm_module/ngx_wasm_module/work/downloads/v8-10.5.18/wasm.h'
'/home/runner/work/v8-10.5.18/lib/libwee8.a' -> '/home/runner/work/ngx_wasm_module/ngx_wasm_module/work/downloads/v8-10.5.18/libwee8.a'
'/home/runner/work/v8-10.5.18/include/cwabt.h' -> '/home/runner/work/ngx_wasm_module/ngx_wasm_module/work/downloads/v8-10.5.18/cwabt.h'
'/home/runner/work/v8-10.5.18/lib/libcwabt.a' -> '/home/runner/work/ngx_wasm_module/ngx_wasm_module/work/downloads/v8-10.5.18/libcwabt.a'

However, these don't seem to be found in subsequent runs, so the "Setup cache" CI step, which uses plain work/downloads, is presumably only caching the top-level one?...

I can do some simple tweaks to move the cached V8 assets around, but I thought I'd write down this summary of the situation first in case there's something wrong going on with the caching of work/ in general that might need to be fixed instead.

[thibaultcha]

I too had noticed the V8 caching wasn't working (the CI times of course), glad you got it!