[libc] Add a cacheline size of arm target.

It is set arbitrarily at 32 now. It can be adjusted as required in
future.

Author: Siva Chandra Reddy

libc/src/string/memory_utils/utils.h

@@ -17,6 +17,8 @@
 // time.
 #if defined(LLVM_LIBC_ARCH_AARCH64) || defined(LLVM_LIBC_ARCH_X86)
 #define LLVM_LIBC_CACHELINE_SIZE 64
+#elif defined(LLVM_LIBC_ARCH_ARM)
+#define LLVM_LIBC_CACHELINE_SIZE 32
 #else
 #error "Unsupported platform for memory functions."
 #endif