dhrystone: Prevent procedure merging

From the Dhrystone RATIONALE:

  o No procedure merging

    Although Dhrystone contains some very short procedures where execution would
    benefit  from  procedure  merging (inlining, macro expansion of procedures),
    procedure merging is not to be used.  The reason is that the  percentage  of
    procedure  and  function  calls  is  part of the "Dhrystone distribution" of
    statements contained in [1].  This restriction does not hold for the  string
    functions  of  the  C  version  since ANSI C allows an implementation to use
    inline code for these functions.

Close #5058.

spec/build/testsuites/benchmarks/dhrystone.yml

@@ -1,6 +1,7 @@
 SPDX-License-Identifier: CC-BY-SA-4.0 OR BSD-2-Clause
 build-type: test-program
-cflags: []
+cflags:
+- -fno-inline
 copyrights:
 - Copyright (C) 2020 embedded brains GmbH & Co. KG
 cppflags: []