Improve custom toolchain to support unknown compiler/linker.

[waruqi]

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

But I haven't figured out how to design the API yet.

Describe the solution you'd like

.

Describe alternatives you've considered

No response

Additional context

No response

[ArgoreOfficial]

One idea I had would be to separate tools from the toolchain, giving essentially full control over the entire pipeline

tool("mycxx")
    set_bindir("path/to/bin") -- "mycxx.exe" is assumed
    set_kind("file")          -- run this per file
    set_filetypes("cpp")      -- run this only on .cpp files
    set_extension("o")        -- generate .o file for linker/archiver
    set_format("gcc")         -- use default gcc format 
                                --> mycxx -c -o file.o main.cpp -Wall

    -- alternatively, for custom formats
    set_format({ "-key $(key)", "-c -o $(outfile)", "$(flags)", "$(file)" })
        --> mycxx -key P -c -o main.o -Wall main.cpp
tool_end()

key thing to note here would be the set_kind, which would specify if the tool is run once per file, like compilers, or once per output, like the linker
it would determine what is input into the $(file) or $(files) keys.

creating the toolchain would then be more like

toolchain("MyToolchain") -- tools are run in order they are added
    add_tool("mycxx")
    add_tool("myar", { kind = "static" }) -- not sure how kinds should be handeled
    add_tool("myld", { kind = "binary" })
toolchain_end()

target("project")
    set_kind("binary")
    add_files("src/main.cpp")

    set_toolchain("MyToolchain")
    set_toolvar("key", "P") -- user variable
    set_flag("-Wall")
target_end()

In some aspects it's similar to the rule API.
This would at least satisfy the needs for some Sony platforms I've worked with.

This tool api could then be extended to other areas, like custom debuggers or specific platform tools

debugger("MyDebugger")
    set_filetypes("elf")
    add_tool("mydbg")
debugger_end()

target("project")
    set_kind("binary")
    add_files("src/main.cpp")

    set_toolchain("MyToolchain")
    set_toolchain("MyDebugger")
    set_toolvar("key", "P") -- user variable
    set_flag("-Wall")
target_end()

[waruqi]

Now we can add whole custom unknown toolchain. But no docs now. https://github.com/xmake-io/xmake/tree/dev/tests/apis/custom_toolchain