clang-tidy bugprone-sizeof-expression

this was not really testing anything before, because it was doing
   sizeof(char*)
which is 4 or 8

Change-Id: I7eccdd3c6ae14a6fabb27202737fdb2fd12663dc
Reviewed-on: https://gerrit.libreoffice.org/60182
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

sal/qa/rtl/alloc/rtl_alloc.cxx

@@ -155,7 +155,7 @@ public:
 
     void test()
     {
-        const char *sample = "Hello World";
+        const char sample[] = "Hello World";
         std::vector<OUString> aStrings;
 
         rtl_alloc_preInit(true);
@@ -168,7 +168,7 @@ public:
             for (int i = 1; i < 4096; i += 8)
             {
                 OUStringBuffer aBuf(i);
-                aBuf.appendAscii(sample, (i/8) % (sizeof(sample)-1));
+                aBuf.appendAscii(sample, (i/8) % (SAL_N_ELEMENTS(sample)-1));
                 OUString aStr = aBuf.makeStringAndClear();
                 aStrings.push_back(aStr);
             }