Define __NR_perf_event_open if not found in asm/unistd.h

$ grep -Rl __NR_perf_event_open ndk/android-ndk-r8b/platforms
ndk/android-ndk-r8b/platforms/android-9/arch-x86/usr/include/asm/unistd_32.h
ndk/android-ndk-r8b/platforms/android-14/arch-x86/usr/include/asm/unistd_32.h

Not found __NR_perf_event_open in android-ndk-r8b for arch-arm target.