[lsan] Mark 2 new lsan tests unsupported on arm-linux

These tests were added in:
1daa48f0
59e422c9

malloc_zero.c and realloc_too_big.c fail when only
leak sanitizer is enabled.
http://lab.llvm.org:8011/#/builders/59/builds/1635
(also in an armv8 32 bit build)

(I would XFAIL them but the same test is run with
address and leak sanitizer enabled and that one does
pass)