EnhancementRequest: check_compiler_flag() should understand the "LINKER:" prefix
https://cmake.org/cmake/help/latest/module/CheckSourceCompiles.html
E.g.
check_compiler_flag(C LINKER:--thinlto-jobs=8 CHECK_VAR)
is translated literally to "LINKER:--thinlto-jobs=8" in the generated compiler call, instead of "-Wl,--thinlto-jobs=8"