Index: nix/corepkgs/buildenv/builder.pl.in
===================================================================
--- nix/corepkgs/buildenv/builder.pl.in	(revision 25667)
+++ nix/corepkgs/buildenv/builder.pl.in	(working copy)
@@ -42,7 +42,8 @@
             $srcFile =~ /\/site.py$/ ||
             $srcFile =~ /\/site.pyc$/ ||
             $srcFile =~ /\/info\/dir$/ ||
-            $srcFile =~ /\/log$/)
+            $srcFile =~ /\/log$/) ||
+            $relName =~ /^\/share\/icons\/.*\/icon-theme\.cache/;
         {
             # Do nothing.
 	}
Index: nixpkgs/pkgs/build-support/buildenv/builder.pl
===================================================================
--- nixpkgs/pkgs/build-support/buildenv/builder.pl	(revision 25663)
+++ nixpkgs/pkgs/build-support/buildenv/builder.pl	(working copy)
@@ -17,7 +17,7 @@
     $path = "/" if $path eq "";
     foreach my $elem (@pathsToLink) {
         return 1 if
-            $elem eq "/" || 
+            $elem eq "/" ||
             (substr($path, 0, length($elem)) eq $elem
              && (($path eq $elem) || (substr($path, length($elem), 1) eq "/")));
     }
@@ -38,13 +38,13 @@
     opendir DIR, "$target" or die "cannot open `$target': $!";
     my @names = readdir DIR or die;
     closedir DIR;
-    
+
     foreach my $name (@names) {
         next if $name eq "." || $name eq "..";
         findFiles("$relName/$name", "$target/$name", $name, $ignoreCollisions);
     }
 }
-    
+
 sub findFiles {
     my ($relName, $target, $baseName, $ignoreCollisions) = @_;
 
@@ -55,7 +55,8 @@
         $relName =~ /info\/dir/ ||
         ( $relName =~ /^\/share\/mime\// && !( $relName =~ /^\/share\/mime\/packages/ ) ) ||
         $baseName eq "perllocal.pod" ||
-        $baseName eq "log";
+        $baseName eq "log" ||
+        $relName =~ /^\/share\/icons\/.*\/icon-theme\.cache/;
 
     my $oldTarget = $symlinks{$relName};
 
@@ -75,7 +76,7 @@
 
     findFilesInDir($relName, $oldTarget, $ignoreCollisions) unless $oldTarget eq "";
     findFilesInDir($relName, $target, $ignoreCollisions);
-    
+
     $symlinks{$relName} = ""; # denotes directory
 }