The commit 3ab6209a3f had the undesired
effect of retaining every `__imp_` symbol, even if it isn't referenced
in any way. Add a testcase to observe this behaviour, to serve as
a reference point if this behaviour were to be improved later.
Port the testcase from b963c0b658 from
the llvm/LTO testsuite into LLD as a preparation for changing that fix;
the moved testcase has a comment for one case which doesn't work
currently.
The testcase is ported mostly as is, but with symbol mangling
simplified, rewriting function names from MSVC C++ mangling to plain
C, and unnecessary debug info is removed.
Add a case of a dllimported data symbol, in addition to the existing
call of a dllimported function.
Also extend the testcase to test combinations of both regular
object files and LTO objects. Leave out one combination which currently
fails, with a comment.
6a323e7ec3