Add /opt/homebrew to search path on Apple Silicon

This is default directory for Homebrew on Apple Silicon. Intel Mac installs into `/usr/local`, which is in our default path.

Co-authored-by: Caleb Land <caleb@land.fm>

Author: andyundso

CHANGELOG.md

@@ -4,6 +4,7 @@
 * Fix segfault when asking if client was dead after closing it. Fixes #519.
 * Mark `alloc` function as undefined on `TinyTds::Result`. Fixes #515.
 * Fix Gem installation on Windows by adding default freetds msys path. Fixes #522
+* Search for `freetds` in `/opt/homebrew` when installing on Apple Silicon. Fixes #484, #492 and #508.
 
 ## 2.1.5
 

ext/tiny_tds/extconf.rb

@@ -35,6 +35,19 @@ def do_help
   /usr/local
 )
 
+if RbConfig::CONFIG['host_os'] =~ /darwin/i
+  # Ruby below 2.7 seems to label the host CPU on Apple Silicon as aarch64
+  # 2.7 and above print is as ARM64
+  target_host_cpu = Gem::Version.new(RUBY_VERSION) < Gem::Version.new('2.7') ? 'aarch64' : 'arm64'
+
+  if RbConfig::CONFIG['host_cpu'] == target_host_cpu
+    # Homebrew on Apple Silicon installs into /opt/hombrew
+    # https://docs.brew.sh/Installation
+    # On Intel Macs, it is /usr/local, so no changes necessary to DIRS
+    DIRS.unshift("/opt/homebrew")
+  end
+end
+
 if ENV["RI_DEVKIT"] && ENV["MINGW_PREFIX"] # RubyInstaller Support
   DIRS.unshift(File.join(ENV["RI_DEVKIT"], ENV["MINGW_PREFIX"]))
 end