Remove IRLinker::linkNamedMDNodes() assert

It was added in llvm#157045, but will fail if there are duplicated nodes in
DstM already, as illustrated by the test. See comments on the PR.

Author: zmodem

llvm/lib/Linker/IRMover.cpp

@@ -1152,7 +1152,6 @@ void IRLinker::linkNamedMDNodes() {
       if (Inserted.insert(MD).second)
         DestNMD->addOperand(MD);
     }
-    assert(Inserted.size() == DestNMD->getNumOperands());
   }
 }
 

llvm/test/ThinLTO/X86/Inputs/import-metadata.ll

@@ -15,9 +15,13 @@ entry:
 !llvm.module.flags = !{!2, !3}
 !llvm.md = !{!5}
 
+; IRLinker shouldn't assert about duplicated operands.
+!llvm.ident = !{!6, !6}
+
 !0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, enums: !4)
 !1 = !DIFile(filename: "foo.cpp", directory: "tmp")
 !2 = !{i32 2, !"Dwarf Version", i32 4}
 !3 = !{i32 2, !"Debug Info Version", i32 3}
 !4 = !{}
 !5 = !{!4}
+!6 = !{!"foo"}

llvm/test/ThinLTO/X86/import-metadata.ll

@@ -33,9 +33,13 @@ define i32 @main() {
 !llvm.module.flags = !{!2, !3}
 !llvm.md = !{!5}
 
+; IRLinker shouldn't assert about duplicated operands.
+!llvm.ident = !{!6, !6}
+
 !0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, enums: !4)
 !1 = !DIFile(filename: "main.cpp", directory: "tmp")
 !2 = !{i32 2, !"Dwarf Version", i32 4}
 !3 = !{i32 2, !"Debug Info Version", i32 3}
 !4 = !{}
 !5 = !{!4}
+!6 = !{!"foo"}