tools/elfutils: use locally declared static reallocarray()

tools/elfutils: use locally declared static reallocarray()

On macOS, stdlib.h in the standard include paths does not provide
reallocarray() while both elfutils and gnulib do, however they are
declared differently, leading to an error:

  ./system.h:101:1: error: static declaration of 'reallocarray' follows non-static declaration
  reallocarray (void *ptr, size_t nmemb, size_t size)

A normal "configure && make" build cycle results in both declarations
being enabled as a result of both elfutils and gnulib having completely
separate configure checks where gnulib uses an internal placeholder symbol
HAVE_REALLOCARRAY, and elfutils uses a standard autoconf macro
HAVE_DECL_REALLOCARRAY.

Fix this by excluding the import of the reallocarray module which causes
gnulib checks in the configure stage to not even consider whether to
declare reallocarray later on, so the decision is only between the
standard include stdlib.h and the elfutils header.

Tested-by: Georgi Valkov <gvalkov@gmail.com> # MacOS
Signed-off-by: Michael Pratt <mcpratt@pm.me>
Signed-off-by: Tony Ambardar <itugrok@yahoo.com>