Support set_languages("cxx20") for intellisense

[maximegmd]

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

Currently I can only use set_languages("cxx17") but I need c++latest in visual studio.
Using

set_languages("cxx17")
add_cxflags("/std:c++latest")

Builds but generates the warning:

2>cl : Command line warning D9025: overriding '/std:c++17' with '/std:c++latest'

Using only add_cxflags builds but Intellisense then assumes C++14 failing to parse files correctly.

Using

set_languages("cxx20")

Builds but breaks intellisense.

Describe the solution you'd like

set_languages("cxxlatest")

[waruqi]

you need only set to cxx20, it will be mapped to c++latest or c++20

xmake/xmake/modules/core/tools/cl.lua

Line 227 in 243ddec

, cxx20 = {"-std:c++20", "-std:c++latest"}

Builds but breaks intellisense

vsxmake? see #1105