garray: Change free/unref semantics under static analysis

Recent changes to `GPtrArray` and/or Coverity mean that Coverity is now
assuming that `g_ptr_array_free (my_array, TRUE)` can leak memory. This
is true in the case that `g_ptr_array_ref (my_array)` has been called
elsewhere, but Coverity never actually verifies that.

Very little (or no?) GLib code mixes `g_ptr_array_free()` with
`g_ptr_array_{ref,unref}()`, so this isn’t a problem in practice.

However, it has created a hundred or more false positives in Coverity
(as pointer arrays are widely used within GLib and GIO), which is a
complete pain.

Before taking the dramatic step of ditching Coverity due to its
atrocious false positive rate, let’s try changing the semantics of
`g_ptr_array_free()` only when running under Coverity.

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>

glib/garray.c

@@ -1555,9 +1555,14 @@ g_ptr_array_free (GPtrArray *array,
 
   /* if others are holding a reference, preserve the wrapper but
    * do free/return the data
+   *
+   * Coverity doesn’t understand this and assumes it’s a leak, so comment this
+   * out.
    */
+#ifndef __COVERITY__
   if (!g_atomic_ref_count_dec (&rarray->ref_count))
     flags |= PRESERVE_WRAPPER;
+#endif
 
   return ptr_array_free (array, flags);
 }