[clangd] Add missing GoToStmt in FindTarget.

[hokein]

Summary

so that go-to-def on label can work.

clang-tools-extra/clangd/FindTarget.cpp

struct Visitor : public ConstStmtVisitor<Visitor> {
         for (const DesignatedInitExpr::Designator &D :
              llvm::reverse(DIE->designators()))
           if (D.isFieldDesignator()) {
             Outer.add(D.getField(), Flags);
             // We don't know which designator was intended, we assume the outer.
             break;
           }
       }
+      void VisitGotoStmt(const GotoStmt *Goto) {
+        if (auto *LabelDecl = Goto->getLabel())
+          Outer.add(LabelDecl, Flags);
+      }
+      void VisitLabelStmt(const LabelStmt *Label) {
+        if (auto *LabelDecl = Label->getDecl())
+          Outer.add(LabelDecl, Flags);
+      }
       void
       VisitCXXDependentScopeMemberExpr(const CXXDependentScopeMemberExpr *E) {
         const Type *BaseType = E->getBaseType().getTypePtrOrNull();
         if (E->isArrow()) {
           BaseType = getPointeeType(BaseType);
         }
         for (const NamedDecl *D : getMembersReferencedViaDependentName(
                  BaseType, [E](ASTContext &) { return E->getMember(); },

clang-tools-extra/clangd/unittests/FindTargetTests.cpp

Code = R"cpp(
     void operator()(int n);
     };
     void test() {
       X x;
       x[[(123)]];
     }
   )cpp";
   EXPECT_DECLS("CXXOperatorCallExpr", "void operator()(int n)");
+
+  Code = R"cpp(
+    void test() {
+      goto [[label]];
+    label:
+      return;
+    }
+  )cpp";
+  EXPECT_DECLS("GotoStmt", "label:");
+  Code = R"cpp(
+    void test() {
+    [[label]]:
+      return;
+    }
+  )cpp";
+  EXPECT_DECLS("LabelStmt", "label:");
 }
 
 TEST_F(TargetDeclTest, Recovery) {
   Code = R"cpp(
     // error-ok: testing behavior on broken code
     int f();
     int f(int, int);
     int x = [[f]](42);