Use execvp rather then execv in exec_process

[sbc100]

When this code was added in #20909 it broke users who were doing EM_COMPILER_WRAPPER=cache since it was not using PATH to find the executable (unlike the subprocess module).

Fixes: #22736

[kripken]

(do we have ccache on the CI machines?)

[sbc100]

(do we have ccache on the CI machines?)

Probably not.. so I guess we can expect to see this file on test-other. Lets see. I'll add it once that is confirmed.

[kleisauke]

Just wondering, is EM_COMPILER_WRAPPER=ccache recommended over _EMCC_CCACHE=1? I've been using the latter (internal) setting for a while now:
https://github.com/kleisauke/wasm-vips/blob/v0.0.10/Dockerfile#L45-L47

[sbc100]

Just wondering, is EM_COMPILER_WRAPPER=ccache recommended over _EMCC_CCACHE=1? I've been using the latter (internal) setting for a while now: https://github.com/kleisauke/wasm-vips/blob/v0.0.10/Dockerfile#L45-L47

Hmm.. I can't remember exactly that EMCC_CCACHE was needed, but it works slightly differently. EM_COMPILER_WRAPPER can be used to inject any compiler wrapper, not just ccache. It gets injected inside the python driver and it adds the wrapper to the internal clang calls.

_EMCC_CCACHE inject explicitly cache only and it works in the shell/bat files and adds the wrapper before emcc rather than clang. So if you you use _EMCC_CCACHE then ccache itself will see emcc as the compiler but if you use EM_COMPILER_WRAPPER then ccache will see clang as the compiler. I think _EMCC_CCACHE might require a patched version of ccache?

[kleisauke]

Thanks for the information!

I think _EMCC_CCACHE might require a patched version of ccache?

It seems to work without any patches, though I haven't tested it extensively. emsdk also provides a patched version of ccache through the ccache-git-emscripten-64bit target.
https://github.com/emscripten-core/emsdk/blob/3.1.69/emsdk_manifest.json#L678-L688

(the same question was raised in #13498 (comment))

[sbc100]

Sounds like performance is that reason to prefer _EMCC_CCACHE. I do wonder if the difference is still as significant these days.