Fix javac-21 compiler warnings

debian/patches/fix-javac-21-warnings.patch

+--- a/javacutil/src/main/java/org/checkerframework/javacutil/trees/TreeBuilder.java
++++ b/javacutil/src/main/java/org/checkerframework/javacutil/trees/TreeBuilder.java
+@@ -71,6 +71,7 @@
+      * @param iterableExpr an expression whose type is a subtype of Iterable
+      * @return a MemberSelectTree that accesses the iterator() method of the expression
+      */
++    @SuppressWarnings("cast")
+     public MemberSelectTree buildIteratorMethodAccess(ExpressionTree iterableExpr) {
+         DeclaredType exprType =
+                 (DeclaredType) TypesUtils.upperBound(TreeUtils.typeOf(iterableExpr));
+@@ -140,6 +141,7 @@
+      * @param iteratorExpr an expression whose type is a subtype of Iterator
+      * @return a MemberSelectTree that accesses the hasNext() method of the expression
+      */
++    @SuppressWarnings("cast")
+     public MemberSelectTree buildHasNextMethodAccess(ExpressionTree iteratorExpr) {
+         DeclaredType exprType = (DeclaredType) TreeUtils.typeOf(iteratorExpr);
+         assert exprType != null : "expression must be of declared type Iterator<>";
+@@ -176,6 +178,7 @@
+      * @param iteratorExpr an expression whose type is a subtype of Iterator
+      * @return a MemberSelectTree that accesses the next() method of the expression
+      */
++    @SuppressWarnings("cast")
+     public MemberSelectTree buildNextMethodAccess(ExpressionTree iteratorExpr) {
+         DeclaredType exprType = (DeclaredType) TreeUtils.typeOf(iteratorExpr);
+         assert exprType != null : "expression must be of declared type Iterator<>";
+@@ -231,6 +234,7 @@
+      * @param expression the array expression whose length is being accessed
+      * @return a MemberSelectTree to dereference the length of the array
+      */
++    @SuppressWarnings("cast")
+     public MemberSelectTree buildArrayLengthAccess(ExpressionTree expression) {
+ 
+         return (JCTree.JCFieldAccess)
+@@ -404,6 +408,7 @@
+      * @param expr an expression whose type is a boxed type
+      * @return a MemberSelectTree that accesses the valueOf() method of the expression
+      */
++    @SuppressWarnings("cast")
+     public MemberSelectTree buildValueOfMethodAccess(Tree expr) {
+         TypeMirror boxedType = TreeUtils.typeOf(expr);
+ 
+@@ -453,6 +458,7 @@
+      * @param expr an expression whose type is a boxed type
+      * @return a MemberSelectTree that accesses the *Value() method of the expression
+      */
++    @SuppressWarnings("cast")
+     public MemberSelectTree buildPrimValueMethodAccess(Tree expr) {
+         TypeMirror boxedType = TreeUtils.typeOf(expr);
+         TypeElement boxedElement = (TypeElement) ((DeclaredType) boxedType).asElement();