Recognize ld with toolchain prefix (#13960)

Teach CMAKE_PARSE_IMPLICIT_LINK_INFO to recognize linker invocations
of the form "<toolchain-prefix>-ld" e.g. "x86_64-pc-linux-gnu-ld".
Merge topic 'implicit-linker-detection' into next

a2bc47d Recognize ld with toolchain prefix (#13960)