GNU ld silently accepts the -rpath option for Windows targets, as a
no-op.
This has lead to some build systems (and users) passing this option
while building for Windows/MinGW, even if Windows doesn't have any
concept like rpath.
Older versions of Conan did include -rpath in the pkg-config files it
generated, see e.g.
17c58f0c61/conans/client/generators/pkg_config.py (L104-L114)
and
17c58f0c61/conans/client/build/compiler_flags.py (L26-L34)
- and see https://github.com/mstorsjo/llvm-mingw/issues/300 for user
reports about this issue.
Recognize the option in LLD for MinGW targets, to improve drop-in
compatibility compared to GNU ld, but produce a warning to alert users
that the option really has no effect for these targets.
(cherry picked from commit 69f76c782b554a004078af6909c19a11e3846415)
6dbc0e236b