Darwin/ARM64: Set default mcpu target (#36624)

And unconditionally require the CRC32 extension on this platform.
All current and future chips should have it.

Make.inc

@@ -777,6 +777,11 @@ ifeq ($(ARCH),amd64)
 override ARCH := x86_64
 endif
 
+# We map arm64 (Apple spelling) to aarch64 to avoid having to deal with both spellings everywhere
+ifeq ($(ARCH),arm64)
+override ARCH := aarch64
+endif
+
 ifeq ($(ARCH),i386)
 BINARY:=32
 ISX86:=1
@@ -853,6 +858,10 @@ endif
 ifneq (,$(findstring aarch64,$(ARCH)))
 OPENBLAS_DYNAMIC_ARCH:=0
 OPENBLAS_TARGET_ARCH:=ARMV8
+ifeq ($(OS),Darwin)
+# Apple Chips are all at least A12Z
+MCPU:=apple-a12
+endif
 endif
 
 # Set MARCH-specific flags

src/crc32c.c

@@ -45,7 +45,7 @@
 #include "julia_internal.h"
 #include "processor.h"
 
-#ifdef _CPU_AARCH64_
+#if defined(_CPU_AARCH64_) && defined(_OS_LINUX_)
 #  include <sys/auxv.h>
 #endif
 
@@ -331,7 +331,11 @@ JL_DLLEXPORT uint32_t jl_crc32c(uint32_t crc, const char *buf, size_t len)
 {
     return crc32c_armv8(crc, buf, len);
 }
-#  else
+#  elif defined(_OS_DARWIN_)
+// All Apple chips that run Darwin should have crc32 support.
+// If that ever changes for some reason, this could be detected via the hw.optional.crc32 sysctl
+#  error Darwin/ARM64, but no CRC32 support?
+#  elif defined(_OS_LINUX_)
 static crc32c_func_t crc32c_dispatch(unsigned long hwcap)
 {
     if (hwcap & (1 << JL_AArch64_crc))
@@ -341,6 +345,8 @@ static crc32c_func_t crc32c_dispatch(unsigned long hwcap)
 // For ifdef detection below
 #    define crc32c_dispatch() crc32c_dispatch(getauxval(AT_HWCAP))
 #    define crc32c_dispatch_ifunc "crc32c_dispatch"
+#  else
+#  warning CRC32 feature detection not implemented for this OS. Falling back to software version.
 #  endif
 #else
 // If we don't have any accelerated version to define, just make the _sw version define