8287834: Add SymbolLookup::or method

Reviewed-by: psandoz

src/java.base/share/classes/java/lang/foreign/SymbolLookup.java

@@ -129,6 +129,28 @@ public interface SymbolLookup {
      */
     Optional<MemorySegment> find(String name);
 
+    /**
+     * {@return a composed symbol lookup that returns result of finding the symbol with this lookup if found,
+     * otherwise returns the result of finding the symbol with the other lookup}
+     *
+     * @apiNote This method could be used to chain multiple symbol lookups together, e.g. so that symbols could
+     * be retrieved, in order, from multiple libraries:
+     * {@snippet lang = java:
+     * var lookup = SymbolLookup.libraryLookup("foo", arena)
+     *         .or(SymbolLookup.libraryLookup("bar", arena))
+     *         .or(SymbolLookup.loaderLookup());
+     *}
+     * The above code creates a symbol lookup that first searches for symbols in the "foo" library. If no symbol is found
+     * in "foo" then "bar" is searched. Finally, if a symbol is not found in neither "foo" nor "bar", the {@linkplain
+     * SymbolLookup#loaderLookup() loader lookup} is used.
+     *
+     * @param other the symbol lookup that should be used to look for symbols not found in this lookup.
+     */
+    default SymbolLookup or(SymbolLookup other) {
+        Objects.requireNonNull(other);
+        return name -> find(name).or(() -> other.find(name));
+    }
+
     /**
      * Returns a symbol lookup for symbols in the libraries associated with the caller's class loader.
      * <p>