interp: do not rely on fixed type names

After merging multiple LLVM modules into one, types may have been
renamed. Therefore, the interp package should not rely on types to have
any particular name.

interp/frame.go

@@ -283,6 +283,7 @@ func (fr *frame) evalBasicBlock(bb, incoming llvm.BasicBlock, indent string) (re
 					PkgName:   fr.packagePath,
 					KeySize:   int(keySize),
 					ValueSize: int(valueSize),
+					MapType:   inst.Type().ElementType(),
 				}
 			case callee.Name() == "runtime.hashmapStringSet":
 				// set a string key in the map
@@ -350,7 +351,7 @@ func (fr *frame) evalBasicBlock(bb, incoming llvm.BasicBlock, indent string) (re
 				global.SetLinkage(llvm.InternalLinkage)
 				global.SetGlobalConstant(true)
 				global.SetUnnamedAddr(true)
-				stringType := fr.Mod.GetTypeByName("runtime._string")
+				stringType := inst.Type()
 				retPtr := llvm.ConstGEP(global, getLLVMIndices(fr.Mod.Context().Int32Type(), []uint32{0, 0}))
 				retLen := llvm.ConstInt(stringType.StructElementTypes()[1], uint64(len(result)), false)
 				ret := llvm.ConstNull(stringType)