Prefetch on macos (#9875)

## Problem

Prefetch is disabled at MacODS because `posix_fadvise` is not available.
But Neon prefetch is not using this function and for testing at MacOS is
it very convenient that prefetch is available.

## Summary of changes

Define `USE_PREFETCH` in Makefile.

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Co-authored-by: Konstantin Knizhnik <[email protected]>

Author: knizhnik

Makefile

@@ -38,6 +38,7 @@ ifeq ($(UNAME_S),Linux)
 	# Seccomp BPF is only available for Linux
 	PG_CONFIGURE_OPTS += --with-libseccomp
 else ifeq ($(UNAME_S),Darwin)
+	PG_CFLAGS += -DUSE_PREFETCH
 	ifndef DISABLE_HOMEBREW
 		# macOS with brew-installed openssl requires explicit paths
 		# It can be configured with OPENSSL_PREFIX variable