[wasm] Investigate emscripten cache usage

[pavelsavara]

Updated: now we have the cache in a separate nuget.

The cache nuget/pack will typically be installed in a non-user-writable location.

• how does this affect user builds? Command line, and VS.
• When might emcc try to write to the cache?
• Does emsdk support a "fallback" cache that could be in a user-writable location?
• TODO: Make the dotnet installation non-writeable when running Wasm.Build.Tests

Currently it's caching for both Debug/Release configurations into the same folder.

cache:INFO: generating system library: sysroot\lib\wasm32-emscripten\libc_rt_wasm.a... (this will be cached in "D:\runtime\src\mono\wasm\emsdk\upstream\emscripten\cache\sysroot\lib\wasm32-emscripten\libc_rt_wasm.a" for subsequent builds)

Questions:

• What does emcc use as keys for the cache? Can it differentiate between Debug/Release? (path? hash?)
• If it can't then what else do we need to split the cache on?

Proposed solution

Add --cache <dir> where dir is something like upstream\emscripten\cache-<configuration>\

Tagging subscribers to 'arch-wasm': @lewing
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Issue Details

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Currently it's caching for both configurations into the same folder.

cache:INFO: generating system library: sysroot\lib\wasm32-emscripten\libc_rt_wasm.a... (this will be cached in "D:\runtime\src\mono\wasm\emsdk\upstream\emscripten\cache\sysroot\lib\wasm32-emscripten\libc_rt_wasm.a" for subsequent builds)

Proposed solution

Add --cache <dir> where dir is something like upstream\emscripten\cache-<configuration>\

Author:	pavelsavara
Assignees:	-
Labels:	arch-wasm
Milestone:	-

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[lewing]

The cache situation needs to be fixed very soon.

Tagging subscribers to this area:
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Currently it's caching for both configurations into the same folder.

cache:INFO: generating system library: sysroot\lib\wasm32-emscripten\libc_rt_wasm.a... (this will be cached in "D:\runtime\src\mono\wasm\emsdk\upstream\emscripten\cache\sysroot\lib\wasm32-emscripten\libc_rt_wasm.a" for subsequent builds)

Proposed solution

Add --cache <dir> where dir is something like upstream\emscripten\cache-<configuration>\

Author:	pavelsavara
Assignees:	radekdoulik
Labels:	arch-wasm, area-VM-meta-mono
Milestone:	6.0.0