fix: exclude APIs that dup given file descriptors from WASI builds

WASI doesn't support `dup(2)` system call, so we cannot implement the
`print_dot_graph` and `print_dot_graphs` functions with exactly the same
semantics as in other platforms.

(cherry picked from commit 94a8262110)

lib/src/tree.c

@@ -148,7 +148,7 @@ void ts_tree_print_dot_graph(const TSTree *self, int fd) {
   fclose(file);
 }
 
-#else
+#elif !defined(__wasi__) // WASI doesn't support dup
 
 #include <unistd.h>
 
@@ -162,4 +162,11 @@ void ts_tree_print_dot_graph(const TSTree *self, int file_descriptor) {
   fclose(file);
 }
 
+#else
+
+void ts_tree_print_dot_graph(const TSTree *self, int file_descriptor) {
+  (void)self;
+  (void)file_descriptor;
+}
+
 #endif