Rollup merge of rust-lang#144703 - daltenty:daltenty/extern-weak, r=Noratrieb

[test][AIX] ignore extern_weak linkage test

The AIX linkage model doesn't support ELF-style extern_weak semantics, so just skip this test, like other platforms that don't have it.

Author: samueltardieu

tests/ui/linkage-attr/propagate-generic-issue-18804/main.rs

@@ -4,6 +4,7 @@
 
 //@ ignore-emscripten no weak symbol support
 //@ ignore-apple no extern_weak linkage
+//@ ignore-aix no extern_weak linkage
 
 //@ aux-build:lib.rs