CMake now provides the CMAKE_<LANG>_LINK_MODE variable which specify how
the link step is done. So, the CMAKE_<LANG>_USING_LINKER_MODE variable
is no longer needed.
In `Tests/RunCMake/LinkerSelection`, Xcode 16 warns when building the
AppleClassic case:
ld: warning: -ld_classic is deprecated and will be removed
in a future release
Tolerate all build warnings.
Extend commit 96a953b1ed (Add options to specify linker tool, 2023-09-27,
v3.29.0-rc1~577^2) with the `CMAKE_Swift_USING_LINKER_*` variables
needed to support `CMAKE_LINKER_TYPE` for Swift.
Offer the capability, through variable `CMAKE_LINKER_TYPE`, as well as
the target property `LINKER_TYPE` to specify which linker must be used.
The implementation of this capability is specified by variables specific
to the language and linker type: `CMAKE_<LANG>_USING_LINKER_<TYPE>`.
Some definitions are provided as part of `CMake`.
For example, to select the `LLVM` linker rather than the standard one,
the type `LLD` should be specified through the variable `CMAKE_LINKER_TYPE`.
And, on `Apple`, `Linux` and some environments on `Windows`, the variable
`CMAKE_<LANG>_USING_LINKER_LLD` has value `-fuse-ld=lld`. And for `Windows`
environments based on `MSVC`, where the linker is used directly, the tool
`lld-link.exe` will be used rather than `link.exe`.
Fixes: #19174, #24254, #24990