[scudo][standalone] Only use yield on ARMv6K and newer

[benwolsieffer]

Summary

The yield instruction is only available in ARMv6K and newer. It behaves as a
nop on single threaded platforms anyway, so use nop instead on unsupported
architectures.

[benwolsieffer]

Rebase on main

[Chia-hungDuan]

compiler-rt/lib/scudo/standalone/common.h

104–120

FYI, this will be deprecated in D156951

compiler-rt/lib/scudo/standalone/common.h

template <typename T> inline void shuffle(T *A, u32 N, u32 *RandState) {
   u32 State = *RandState;
   for (u32 I = N - 1; I > 0; I--)
     Swap(A[I], A[getRandomModN(&State, I + 1)]);
   *RandState = State;
 }
 
 // Hardware specific inlinable functions.
 
 inline void yieldProcessor(u8 Count) {
 #if defined(__i386__) || defined(__x86_64__)
   __asm__ __volatile__("" ::: "memory");
   for (u8 I = 0; I < Count; I++)
     __asm__ __volatile__("pause");
 #elif defined(__aarch64__) || defined(__arm__)
   __asm__ __volatile__("" ::: "memory");
   for (u8 I = 0; I < Count; I++)
+#if __ARM_ARCH >= 6 && !defined(__ARM_ARCH_6__)
+    // yield is supported on ARMv6K and newer
     __asm__ __volatile__("yield");
+#else
+    __asm__ __volatile__("nop");
+#endif
 #endif
   __asm__ __volatile__("" ::: "memory");
 }
 
 // Platform specific functions.
 
 extern uptr PageSizeCached;
 uptr getPageSizeSlow();
 inline uptr getPageSizeCached() {
   // Bionic uses a hardcoded value.
   if (SCUDO_ANDROID)