selftests: breakpoints: allow to cross-compile for aarch64/arm64

To build breakpoint_test_arm64, ARCH value is only tested for "aarch64".
It covers only the native build because it's computed from uname -m output.
For cross-compilation, ARCH is set to arm64 and prevent to cross-compile
the test.
Fix the test to allow both native and cross-compilation of the test.

Note: glibc is missing several of the TRAP_* constants in the userspace
definitions. Specifically TRAP_BRANCH and TRAP_HWBKPT.
See https://sourceware.org/bugzilla/show_bug.cgi?id=21286

Signed-off-by: Fathi Boudra <[e-mail]>
Tested-by: Naresh Kamboju <[e-mail]>
Signed-off-by: Shuah Khan <[e-mail]>

tools/testing/selftests/breakpoints/Makefile

···
 ifeq ($(ARCH),x86)
 TEST_GEN_PROGS := breakpoint_test
 endif
-ifeq ($(ARCH),aarch64)
+ifneq (,$(filter $(ARCH),aarch64 arm64))
 TEST_GEN_PROGS := breakpoint_test_arm64
 endif