Add -Zcodegen-source-order for linkage external tests.

Author: ywxt

tests/ui/linkage-attr/linkage-detect-extern-generated-name-collision.rs

@@ -5,7 +5,10 @@
 //@ build-fail
 //@ aux-build:def_colliding_external.rs
 // FIXME(#83838) codegen-units=1 triggers llvm asserts
-//@ compile-flags: -Ccodegen-units=16
+// FIXME(#144940) `-Zcodegen-source-order` avoids `_rust_extern_with_linkage_collision`
+//                sorted after the main, otherwise it causes an ICE. Remove this option
+//                once this issue fixed.
+//@ compile-flags: -Ccodegen-units=16 -Zcodegen-source-order
 
 extern crate def_colliding_external as dep1;
 
@@ -19,7 +22,7 @@ mod dep2 {
 
 fn main() {
     unsafe {
-       println!("{:p}", &dep1::collision);
+        println!("{:p}", &dep1::collision);
     }
 }
 

tests/ui/linkage-attr/linkage-detect-local-generated-name-collision.rs

@@ -1,6 +1,9 @@
 //@ build-fail
 // FIXME(#83838) codegen-units=1 triggers llvm asserts
-//@ compile-flags: -Ccodegen-units=16
+// FIXME(#144940) `-Zcodegen-source-order` avoids `_rust_extern_with_linkage_collision`
+//                sorted after the main, otherwise it causes an ICE. Remove this option
+//                once this issue fixed.
+//@ compile-flags: -Ccodegen-units=16 -Zcodegen-source-order
 #![feature(linkage)]
 
 mod dep1 {

tests/ui/linkage-attr/linkage-detect-local-generated-name-collision.stderr

@@ -1,5 +1,5 @@
 error: symbol `collision` is already defined
-  --> $DIR/linkage-detect-local-generated-name-collision.rs:10:9
+  --> $DIR/linkage-detect-local-generated-name-collision.rs:13:9
    |
 LL |         pub static collision: *const i32;
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^