Ignore expansion-to-defined warning from dlmalloc include

external/vixl/src/../../../external/dlmalloc/malloc.c:2742:5: error: macro expansion producing 'defined' has undefined behavior [-Werror,-Wexpansion-to-defined]
external/vixl/src/../../../external/dlmalloc/malloc.c:589:22: note: expanded from macro 'USE_LOCKS'
                    (defined(USE_RECURSIVE_LOCKS) && USE_RECURSIVE_LOCKS != 0))

Test: m checkbuild
Bug: 29823425
Change-Id: I38d6947b151a97391b88a32a2b3187e7c4e88660