Allow cross-gdb and gdbserver. This requires removal of an explicit
check that disables gdbserver on android. However, the comment above
that check refers to exec_elf.h, which has been removed since API level
19. It builds fine with current selection of the sample (21). Only
build-tested, hope someone can give it a try and report back.
We can fine tune the check for GDB but I'll leave it for now.
Signed-off-by: Alexey Neyman <stilor@att.net>