config.h.cmake: define HAVE_TBB to 1

Using `#define` instead of `#cmakedefine` resulted in `HAVE_TBB` to be
defined as `TRUE`.  This change makes it defined to `1` instead.

config.h.cmake

@@ -61,7 +61,8 @@
 /* Define to 1 if you have <sys/mman.h>. */
 #cmakedefine HAVE_SYS_MMAN_H 1
 
-#define HAVE_TBB ${HAVE_TBB}
+/* Define to 1 if you have the Threading Building Blocks (TBB) library */
+#cmakedefine HAVE_TBB 1
 
 /* begin private */