[libc] add cpu feature flags for SVE/SVE2/MOPS (llvm#166884)

Add in SVE/SVE2/MOPS features for aarch64 cpus. These features may be
interesting for future memory/math routines.

SVE/SVE2 are now being accepted in more implementations:

```
❯ echo | clang-21 -dM -E - -march=native | grep -i ARM_FEAT
#define __ARM_FEATURE_ATOMICS 1
#define __ARM_FEATURE_BF16 1
#define __ARM_FEATURE_BF16_SCALAR_ARITHMETIC 1
#define __ARM_FEATURE_BF16_VECTOR_ARITHMETIC 1
#define __ARM_FEATURE_BTI 1
#define __ARM_FEATURE_CLZ 1
#define __ARM_FEATURE_COMPLEX 1
#define __ARM_FEATURE_CRC32 1
#define __ARM_FEATURE_DIRECTED_ROUNDING 1
#define __ARM_FEATURE_DIV 1
#define __ARM_FEATURE_DOTPROD 1
#define __ARM_FEATURE_FMA 1
#define __ARM_FEATURE_FP16_SCALAR_ARITHMETIC 1
#define __ARM_FEATURE_FP16_VECTOR_ARITHMETIC 1
#define __ARM_FEATURE_FRINT 1
#define __ARM_FEATURE_IDIV 1
#define __ARM_FEATURE_JCVT 1
#define __ARM_FEATURE_LDREX 0xF
#define __ARM_FEATURE_MATMUL_INT8 1
#define __ARM_FEATURE_NUMERIC_MAXMIN 1
#define __ARM_FEATURE_PAUTH 1
#define __ARM_FEATURE_QRDMX 1
#define __ARM_FEATURE_RCPC 1
#define __ARM_FEATURE_SVE 1
#define __ARM_FEATURE_SVE2 1
#define __ARM_FEATURE_SVE_BF16 1
#define __ARM_FEATURE_SVE_MATMUL_INT8 1
#define __ARM_FEATURE_SVE_VECTOR_OPERATORS 2
#define __ARM_FEATURE_UNALIGNED 1
```
MOPS is another set of extension for string operations, but may not be
generally available for now:
```
❯ echo | clang-21 -dM -E - -march=armv9.2a+mops | grep -i MOPS
#define __ARM_FEATURE_MOPS 1
```

Author: SchrodingerZhu

libc/cmake/modules/LLVMLibCCheckCpuFeatures.cmake

@@ -9,7 +9,7 @@ if(LIBC_TARGET_ARCHITECTURE_IS_X86_64)
   set(ALL_CPU_FEATURES SSE2 SSE4_2 AVX AVX2 AVX512F AVX512BW FMA)
   set(LIBC_COMPILE_OPTIONS_NATIVE -march=native)
 elseif(LIBC_TARGET_ARCHITECTURE_IS_AARCH64)
-  set(ALL_CPU_FEATURES "FullFP16")
+  set(ALL_CPU_FEATURES FullFP16 MOPS SVE SVE2)
   set(LIBC_COMPILE_OPTIONS_NATIVE -mcpu=native)
 endif()
 

libc/cmake/modules/cpu_features/check_MOPS.cpp

@@ -0,0 +1,5 @@
+#include "src/__support/macros/properties/cpu_features.h"
+
+#ifndef LIBC_TARGET_CPU_HAS_MOPS
+#error unsupported
+#endif

libc/cmake/modules/cpu_features/check_SVE.cpp

@@ -0,0 +1,5 @@
+#include "src/__support/macros/properties/cpu_features.h"
+
+#ifndef LIBC_TARGET_CPU_HAS_SVE
+#error unsupported
+#endif

libc/cmake/modules/cpu_features/check_SVE2.cpp

@@ -0,0 +1,5 @@
+#include "src/__support/macros/properties/cpu_features.h"
+
+#ifndef LIBC_TARGET_CPU_HAS_SVE2
+#error unsupported
+#endif

libc/src/__support/macros/properties/cpu_features.h

@@ -18,6 +18,18 @@
 #define LIBC_TARGET_CPU_HAS_FULLFP16
 #endif
 
+#if defined(__ARM_FEATURE_SVE)
+#define LIBC_TARGET_CPU_HAS_SVE
+#endif
+
+#if defined(__ARM_FEATURE_SVE2)
+#define LIBC_TARGET_CPU_HAS_SVE2
+#endif
+
+#if defined(__ARM_FEATURE_MOPS)
+#define LIBC_TARGET_CPU_HAS_MOPS
+#endif
+
 #if defined(__SSE2__)
 #define LIBC_TARGET_CPU_HAS_SSE2
 #define LIBC_TARGET_CPU_HAS_FPU_FLOAT