This commit removes a hack in our ThinLTO passes which removes available
externally functions manually. The [upstream bug][1] has long since been fixed,
so we should be able to rely on LLVM natively for this now!

[1]: https://bugs.llvm.org/show_bug.cgi?id=35736

This commit fixes an issue where multiple custom attributes could not be fed
into a custom derive in some situations with the `use_extern_macros` feature
enabled. The problem was that the macro expander didn't consider that it was
making progress when we were deducing that attributes should be lumped in with
custom derive invocations.

The fix applied here was to track in the expander if our attribute is changing
(getting stashed away elsewhere and replaced with a new invocation). If it is
swapped then it's considered progress, otherwise behavior should remain the
same.

Closes rust-lang#52525

Switch a `mkdir $foo` to `mkdir -p $foo` to handle the case that this script is
being run locally and has previously executed.

fix unsafety: don't call ptr_rotate for ZST

`rotate::ptr_rotate` has a comment saying
```
/// # Safety
///
/// The specified range must be valid for reading and writing.
/// The type `T` must have non-zero size.
```
So we better make sure we don't call it on ZST...

Cc @scottmcm (author of rust-lang#41670)

…=nikomatsakis

rustc: Remove a workaround in ThinLTO fixed upstream

This commit removes a hack in our ThinLTO passes which removes available
externally functions manually. The [upstream bug][1] has long since been fixed,
so we should be able to rely on LLVM natively for this now!

[1]: https://bugs.llvm.org/show_bug.cgi?id=35736

Enable run-pass/sepcomp-lib-lto.rs on Android

rust-lang#18800 is fixed, so it should be safe to restore this test.

Remove duplicate E0396 tests

Resolves FIXME rust-lang#13973 (erroneously marked as rust-lang#13972). A test for E0396 already exists in `test/ui/const-deref-ptr.rs`.

rustc: Fix two custom attributes with custom derive

This commit fixes an issue where multiple custom attributes could not be fed
into a custom derive in some situations with the `use_extern_macros` feature
enabled. The problem was that the macro expander didn't consider that it was
making progress when we were deducing that attributes should be lumped in with
custom derive invocations.

The fix applied here was to track in the expander if our attribute is changing
(getting stashed away elsewhere and replaced with a new invocation). If it is
swapped then it's considered progress, otherwise behavior should remain the
same.

Closes rust-lang#52525

Fix docker/run.sh script when run locally

Switch a `mkdir $foo` to `mkdir -p $foo` to handle the case that this script is
being run locally and has previously executed.

Cleanups

r? @RalfJung