From 2f21de596fa11e6a6113d367393d734ce08208a9 Mon Sep 17 00:00:00 2001
From: Kevin Menard <kevin@nirvdrum.com>
Date: Tue, 30 Apr 2019 13:12:27 -0400
Subject: [PATCH] Fix bad mutable call on a frozen string.

---
 Library/Homebrew/build_environment.rb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Library/Homebrew/build_environment.rb b/Library/Homebrew/build_environment.rb
index 7a991f2be0..ef91c825f0 100644
--- a/Library/Homebrew/build_environment.rb
+++ b/Library/Homebrew/build_environment.rb
@@ -59,7 +59,7 @@ module Homebrew
       s = "#{key}: #{value}"
       case key
       when "CC", "CXX", "LD"
-        s << " => #{Pathname.new(value).realpath}" if File.symlink?(value)
+        s += " => #{Pathname.new(value).realpath}" if File.symlink?(value)
       end
       f.puts s
     end