Rollup merge of #64324 - alexcrichton:share-generics-again, r=michaelwoerister

rustc: Fix mixing crates with different `share_generics`

This commit addresses #64319 by removing the `dylib` crate type from the
list of crate type that exports generic symbols. The bug in #64319
arises because a `dylib` crate type was trying to export a symbol in an
uptream crate but it miscalculated the symbol name of the uptream
symbol. This isn't really necessary, though, since `dylib` crates aren't
that heavily used, so we can just conservatively say that the `dylib`
crate type never exports generic symbols, forcibly removing them from
the exported symbol lists if were to otherwise find them.

The fix here happens in two places:

* First is in the `local_crate_exports_generics` method, indicating that
  it's now `false` for the `Dylib` crate type. Only rlibs actually
  export generics at this point.

* Next is when we load exported symbols from upstream crate. If, for our
  compilation session, the crate may be included from a dynamic library,
  then its generic symbols are removed. When the crate was linked into a
  dynamic library its symbols weren't exported, so we can't consider
  them a candidate to link against.

Overally this should avoid situations where we incorrectly calculate the
upstream symbol names in the face of differnet `share_generics` options,
ultimately...

Closes #64319

src/test/ui/panic-runtime/transitive-link-a-bunch.rs

@@ -7,9 +7,8 @@
 // ignore-wasm32-bare compiled with panic=abort by default
 
 #![no_std]
+#![no_main]
 
 extern crate wants_panic_runtime_unwind;
 extern crate wants_panic_runtime_abort;
 extern crate panic_runtime_lang_items;
-
-fn main() {}

src/test/ui/panic-runtime/want-unwind-got-abort.rs

@@ -4,8 +4,7 @@
 // ignore-wasm32-bare compiled with panic=abort by default
 
 #![no_std]
+#![no_main]
 
 extern crate panic_runtime_abort;
 extern crate panic_runtime_lang_items;
-
-fn main() {}

src/test/ui/panic-runtime/want-unwind-got-abort2.rs

@@ -5,8 +5,7 @@
 // ignore-wasm32-bare compiled with panic=abort by default
 
 #![no_std]
+#![no_main]
 
 extern crate wants_panic_runtime_abort;
 extern crate panic_runtime_lang_items;
-
-fn main() {}