radix tree test suite: Build separate binaries for some tests

To allow developers to run a subset of tests, build separate multiorder
and idr-test binaries which will run just the tests in those files.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Reviewed-by: Rehas Sachdeva <aquannie@gmail.com>
diff --git a/tools/testing/radix-tree/multiorder.c b/tools/testing/radix-tree/multiorder.c
index f79812a..e465a38 100644
--- a/tools/testing/radix-tree/multiorder.c
+++ b/tools/testing/radix-tree/multiorder.c
@@ -633,3 +633,10 @@ void multiorder_checks(void)
 
 	radix_tree_cpu_dead(0);
 }
+
+int __weak main(void)
+{
+	radix_tree_init();
+	multiorder_checks();
+	return 0;
+}