gcc@5: Patch for Xcode 10.2 _Atomic bug

Formula/gcc@5.rb

@@ -8,7 +8,7 @@ class GccAT5 < Formula
   url "https://ftp.gnu.org/gnu/gcc/gcc-5.5.0/gcc-5.5.0.tar.xz"
   mirror "https://ftpmirror.gnu.org/gcc/gcc-5.5.0/gcc-5.5.0.tar.xz"
   sha256 "530cea139d82fe542b358961130c69cfde8b3d14556370b65823d2f91f0ced87"
-  revision 2
+  revision 3
 
   bottle do
     sha256 "3cef0d77229769d75a85b545be64ea74fdca7fe99b78a08025d9523dae2db4c1" => :high_sierra
@@ -57,6 +57,16 @@ class GccAT5 < Formula
     end
   end
 
+  # Patch for Xcode bug, taken from https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89864#c43
+  # This should be removed in the next release of GCC if fixed by apple; this is an xcode bug,
+  # but this patch is a work around committed to GCC trunk
+  if MacOS::Xcode.version >= "10.2"
+    patch do
+      url "https://raw.githubusercontent.com/Homebrew/formula-patches/master/gcc%405/gcc5-xcode10.2.patch"
+      sha256 "6834bec30c54ab1cae645679e908713102f376ea0fc2ee993b3c19995832fe56"
+    end
+  end
+
   def install
     # GCC will suffer build errors if forced to use a particular linker.
     ENV.delete "LD"