rocksdb: disable on arm64 except for Linux

Thanks to Theodore Brockman on Zulip for noticing
on an OSX ARM64 and testing this patch.

Per https://github.com/google/cpu_features/pull/150/files
CMAKE_SYSTEM_PROCESSOR is arm64 on Apple.

Without this, compulation error:

[ 80%] Building CXX object storage/rocksdb/CMakeFiles/rocksdblib.dir/rocksdb/util/crc32c.cc.o
/mariadb/storage/rocksdb/rocksdb/util/crc32c.cc:500:18: error: use of undeclared identifier 'isSSE42'
  has_fast_crc = isSSE42();
                 ^
/mariadb/storage/rocksdb/rocksdb/util/crc32c.cc:1230:7: error: use of undeclared identifier 'isSSE42'
  if (isSSE42()) {
      ^
/mariadb/storage/rocksdb/rocksdb/util/crc32c.cc:1231:9: error: use of undeclared identifier 'isPCLMULQDQ'
    if (isPCLMULQDQ()) {
        ^

This can be reverted when the RocksDB submodule is updated.

https://github.com/facebook/rocksdb/commit/ee4bd4780b321ddb5f92a0f4eb956f2a2ebd60dc

storage/rocksdb/CMakeLists.txt

@@ -44,6 +44,15 @@ IF (WIN32 AND CMAKE_SIZEOF_VOID_P EQUAL 4)
   SKIP_ROCKSDB_PLUGIN("32-Bit Windows are temporarily disabled")
 ENDIF()
 
+#
+# Also, disable on ARM64 when not Linux
+# Requires submodule update to v6.16.3
+# containing commit https://github.com/facebook/rocksdb/commit/ee4bd4780b321ddb5f92a0f4eb956f2a2ebd60dc
+#
+IF(CMAKE_SYSTEM_PROCESSOR MATCHES "(arm64|aarch64)" AND NOT CMAKE_SYSTEM_NAME STREQUAL "Linux")
+  SKIP_ROCKSDB_PLUGIN("ARM64 disabled on all except Linux")
+ENDIF()
+
 # This plugin needs recent C++ compilers (it is using C++11 features)
 # Skip build for the old compilers
 SET(CXX11_FLAGS)