Enable testing nacl-gdb on ARM via gdb_tests
Enable testing nacl-gdb on ARM via gdb_tests

Before this change, gdb_tests for ARM was only enabled on the ARM
hardware bots, so we were only testing ARM NaCl against Ubuntu's
system GDB.  We weren't testing the nacl-gdb from the NaCl toolchains
on ARM (because this nacl-gdb is built for x86), so we didn't notice
nacl-gdb's regression in XML support (which affected ARM but not x86).

Fix this by running the GDB tests under qemu-arm, so that we can test
against nacl-gdb on x86 systems.

The debug stub seems to have a problem with breakpoints on qemu-arm
(sometimes continuing skips breakpoints), so some tests are disabled
for qemu-arm.

BUG=https://code.google.com/p/nativeclient/issues/detail?id=3739
TEST=gdb_tests
R=bradnelson@google.com

Review URL: https://codereview.chromium.org/151043003

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@12690 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client