cts: define mcpu=generic for 32-bit ARM builds

* ARMv8 does not support SWP instructions, so this test is to be
  sure that SWP is emulated. Without this commit, the following
  error is generated on ARMv8 while compiling the CPU Instructions
  test:

error: instruction requires: armv7 or earlier
    asm volatile ( "swp r0, r0, [%0]" : "+r"(ptr) : : "r0" );

* Thank you to Alistair Strachan for finding the problem and
   solution.

Change-Id: Ifd6a29373a387f44dfe06a88b72cc22b46516cfa
diff --git a/tests/tests/os/jni/Android.mk b/tests/tests/os/jni/Android.mk
index bcb9d6f..db9bec8 100644
--- a/tests/tests/os/jni/Android.mk
+++ b/tests/tests/os/jni/Android.mk
@@ -57,4 +57,6 @@
 	LOCAL_CFLAGS += -DARCH_SUPPORTS_SECCOMP
 endif
 
+LOCAL_CPPFLAGS_arm := -mcpu=generic
+
 include $(BUILD_SHARED_LIBRARY)