Package preload files for wasm

[jingkaimori]

Is your feature request related to a problem? Please describe.

Some wasm program needs local asset files when starting. Emscripten provides a 'preload' mechanism to package these file into a .data package. XMake should make this kind of package from the list of install file.

Describe the solution you'd like

target("wasmapp") do
    set_kind("binary")
    add_installfiles("assets/as_1.md")
    add_installfiles("assets/as_2.md", {prefixdir = "doc"})
    add_installfiles("assets/(nest/as_3.md)", {prefixdir = "doc"})
end

emcc wasmapp.cpp -o wasmapp.html --preload-file assets/as_1.md --preload-file assets/as_2@doc/as_2.md--preload-file assets/nest/as_3@doc/nest/as_3.md

Describe alternatives you've considered

No response

Additional context

Usage of package arg of emcc is documented here.

[waruqi]

We should not use add_installfiles, it only for installation. xmake install

but --preload-file is only for building stage.

you can use

target("wasmapp") do
    set_kind("binary")
    add_ldflags({"--preload-file", "src/xxx.md"}, {expand = false, force = true})
    add_ldflags({"--preload-file", "src/xxx2.md"}, {expand = false, force = true})
end

[waruqi]

or you can try this on dev branch xmake update -s dev

target("test5")
    set_kind("binary")
    add_files("src/*.cpp")
    add_values("wasm.preloadfiles", "src/xxx.md")
    add_values("wasm.preloadfiles", "src/xxx2.md")