icestorm: patch out Darwin check for sed.

Nix stdenv includes GNU sed, as you would expect.

Author: kivikakk

icestorm.nix

@@ -18,6 +18,10 @@ stdenv.mkDerivation {
     sha256 = icestorm_git_sha256;
   };
 
+  patches = [
+    ./patches/icebox-Makefile.patch
+  ];
+
   makeFlags = [
     "PREFIX=$(out)"
   ];

patches/icebox-Makefile.patch

@@ -0,0 +1,11 @@
+--- a/icebox/Makefile
++++ b/icebox/Makefile
+@@ -2,7 +2,3 @@
+ 
+-ifneq ($(shell uname -s),Darwin)
+-  SED_I = sed -i
+-else
+-  SED_I = sed -i ''
+-endif
++SED_I = sed -i
+