util: tests: vma test depends on C++11 support

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=106776
Fixes: 943fecc569 ("util: Add a randomized test for the virtual memory allocator")
Tested-by: Vinson Lee <vlee@freedesktop.org>
Reviewed-by: Dylan Baker <dylan@pnwbakers.com>

src/util/Makefile.am

@@ -22,8 +22,11 @@
 SUBDIRS = . \
 	xmlpool \
 	tests/hash_table \
-	tests/string_buffer \
-	tests/vma
+	tests/string_buffer
+
+if HAVE_STD_CXX11
+SUBDIRS += tests/vma
+endif
 
 include Makefile.sources