Improve to detect cross-compilation toolchains

[waruqi]

Roadmap

• Seperate platform and toolchain
  • xmake f -p cross --sdk=xxx [--toolchain=llvm]
• toolchains
  • envs ($CC)
  • llvm https://releases.llvm.org/
  • mingw
  • gnu-rm https://developer.arm.com/tools-and-software/open-source-software/developer-tools/gnu-toolchain/gnu-rm/downloads#
  • Crosstool NG https://crosstool-ng.github.io/
  • sdcc
  • vs
  • clang
  • gcc
  • cross
  • xcode
  • yasm, nasm, fasm
  • go, dlang, rust
  • cuda
• toolchain("xxx") scope description
  • set_sdkdir
  • set_bindir
  • set_toolset("cc", "clang", "gcc"), ld, sh, ar, mm, gc, dcld, ...
  • add_includedirs
  • add_linkdirs
  • add_syslinks
  • add_ldflags
  • add_cxflags ...
  • set_arches
  • set_formats
  • on_load
  • on_check
  • support custom toolchain in project xmake.lua
• platform()
  • set_toolchains
• target()
  • set_toolchains("clang", "yasm") to modify the given toolchain configs
  • set_toolset("cc", "clang") instead of set_toolchain()

备注：重构工具链，实现平台定义和工具链完全分离，提供更好的工具链扩展性，支持对独立工具链完整快速切换，支持对target的单独工具链配置，支持在xmake.lua自定义工具链，内置支持更多常用交叉编译工具链

[waruqi]

Switch the given toolchain in any platform

$ xmake f --toolchain=clang
$ xmake

$ xmake f --toolchain=llvm --sdk=/xxx/llvm
$ xmake

$ xmake f -p cross --sdk=/xxx/llvm
$ xmake

[waruqi]

Custom toolchain in project xmake.lua

-- define toolchain
toolchain("myclang")

    -- mark as standalone toolchain
    set_kind("standalone")
        
    -- set toolset
    set_toolset("cc", "clang")
    set_toolset("cxx", "clang", "clang++")
    set_toolset("ld", "clang++", "clang")
    set_toolset("sh", "clang++", "clang")
    set_toolset("ar", "ar")
    set_toolset("ex", "ar")
    set_toolset("strip", "strip")
    set_toolset("mm", "clang")
    set_toolset("mxx", "clang", "clang++")
    set_toolset("as", "clang")

    add_defines("MYCLANG")

    -- check toolchain
    on_check(function (toolchain)
        return import("lib.detect.find_tool")("clang")
    end)

    -- on load
    on_load(function (toolchain)

        -- get march
        local march = is_arch("x86_64", "x64") and "-m64" or "-m32"

        -- init flags for c/c++
        toolchain:add("cxflags", march)
        toolchain:add("ldflags", march)
        toolchain:add("shflags", march)
        if not is_plat("windows") and os.isdir("/usr") then
            for _, includedir in ipairs({"/usr/local/include", "/usr/include"}) do
                if os.isdir(includedir) then
                    toolchain:add("includedirs", includedir)
                end
            end
            for _, linkdir in ipairs({"/usr/local/lib", "/usr/lib"}) do
                if os.isdir(linkdir) then
                    toolchain:add("linkdirs", linkdir)
                end
            end
        end

        -- init flags for objc/c++  (with ldflags and shflags)
        toolchain:add("mxflags", march)

        -- init flags for asm
        toolchain:add("asflags", march)
    end)

$ xmake f --toolchain=myclang
$ xmake

[waruqi]

Set the different toolchain to the given target

target("test")
    set_toolchains("clang", "yasm")

target("test2")
    set_toolset("cc", "clang")
    set_toolset("ld", "clang++")

[waruqi]

Gnu

GNU Arm Embedded Toolchain

https://developer.arm.com/tools-and-software/open-source-software/developer-tools/gnu-toolchain/gnu-rm

xmake f -p cross --sdk=~/files/gcc-arm-none-eabi-9-2019-q4-major/ --toolchain=gnu-rm
xmake

[waruqi]

Show toolchains

$ xmake show -l toolchains
xcode         Xcode IDE
vs            VisualStudio IDE
yasm          The Yasm Modular Assembler
clang         A C language family frontend for LLVM
go            Go Programming Language Compiler
dlang         D Programming Language Compiler
sdcc          Small Device C Compiler
cuda          CUDA Toolkit
ndk           Android NDK
rust          Rust Programming Language Compiler
llvm          A collection of modular and reusable compiler and toolchain technologies
cross         Common cross compilation toolchain
nasm          NASM Assembler
gcc           GNU Compiler Collection
mingw         Minimalist GNU for Windows
gnu-rm        GNU Arm Embedded Toolchain
envs          Environment variables toolchain
fasm          Flat Assembler