opcache/jit support: Mac M1 build fix

unfortunately host_cpu is set only as `arm`.
adding preprocessor ARM64APPLE for future use to be able to distinguish
 possibly from an usual arm64 board (e.g. not all same registers,
x29/x30 vs fp/lr etc).

Author: devnexen

ext/opcache/config.m4

@@ -58,6 +58,10 @@ if test "$PHP_OPCACHE" != "no"; then
       x86*)
         DASM_ARCH="x86"
         ;;
+      arm*-*-darwin*)
+        DASM_FLAGS="-D ARM64APPLE=1 -D ARM64=1"
+        DASM_ARCH="arm64"
+        ;;
       aarch64*)
         DASM_FLAGS="-D ARM64=1"
         DASM_ARCH="arm64"