ANDROID: Disable UNWINDER_ORC for allmodconfig

CONFIG_UNWINDER_ORC needs a libelf-dev which we unfortunately can't
afford to have in the CI yet.

Switch to different stack unwinder for allmodconfig to work around the
problem temporarily.

Bug: 140224784
Test: allmodconfig build for x86
Change-Id: Id35c222e76cca35aa5e520c1a3d5d88e5cc1da8a
Signed-off-by: Quentin Perret <qperret@google.com>