Ignore musl for no-allocation-before-main test

Author: GnomedDev

tests/ui/runtime/no-allocation-before-main.rs

@@ -5,6 +5,7 @@
 //! -Cprefer-dynamic=no is required as otherwise #[global_allocator] does nothing.
 //@ run-pass
 //@ compile-flags: -Cprefer-dynamic=no
+//@ ignore-musl needs register_dtor_fallback, which allocates.
 
 #[allow(dead_code)]
 #[path = "aborting-alloc.rs"]