fix(internal): fix formatting script for macos

Author: stainless-app[bot]

Rakefile

@@ -58,12 +58,13 @@ end
 desc("Format `*.rbs`")
 multitask(:"format:syntax_tree") do
   find = %w[find ./sig -type f -name *.rbs -print0]
-  inplace = /darwin|bsd/ =~ RUBY_PLATFORM ? %w[-i''] : %w[-i]
+  inplace = /darwin|bsd/ =~ RUBY_PLATFORM ? ["-i", ""] : %w[-i]
   uuid = SecureRandom.uuid
 
   # `syntax_tree` has trouble with `rbs`'s class & module aliases
 
-  sed = xargs + %w[sed -E] + inplace + %w[-e]
+  sed_bin = /darwin/ =~ RUBY_PLATFORM ? "/usr/bin/sed" : "sed"
+  sed = xargs + [sed_bin, "-E", *inplace, "-e"]
   # annotate unprocessable aliases with a unique comment
   pre = sed + ["s/(class|module) ([^ ]+) = (.+$)/# \\1 #{uuid}\\n\\2: \\3/", "--"]
   fmt = xargs + %w[stree write --plugin=rbs --]