xorg.mkfontdir: replace with mkfontscale, which now includes mkfontdir

See:
https://lists.x.org/archives/xorg-announce/2019-March/002960.html

pkgs/servers/x11/xorg/generate-expr-from-tarballs.pl

@@ -26,7 +26,7 @@ my %pcMap;
 my %extraAttrs;
 
 
-my @missingPCs = ("fontconfig", "libdrm", "libXaw", "zlib", "perl", "python", "mkfontscale", "mkfontdir", "bdftopcf", "libxslt", "openssl", "gperf", "m4");
+my @missingPCs = ("fontconfig", "libdrm", "libXaw", "zlib", "perl", "python", "mkfontscale", "bdftopcf", "libxslt", "openssl", "gperf", "m4");
 $pcMap{$_} = $_ foreach @missingPCs;
 $pcMap{"freetype2"} = "freetype";
 $pcMap{"libpng12"} = "libpng";
@@ -157,7 +157,7 @@ while (<>) {
     }
 
     if ($file =~ /AC_PATH_PROG\(MKFONTDIR/) {
-        push @requires, "mkfontdir";
+        push @requires, "mkfontscale";
     }
 
     if ($file =~ /AM_PATH_PYTHON/) {
@@ -173,12 +173,12 @@ while (<>) {
     my $isFont;
 
     if ($file =~ /XORG_FONT_BDF_UTILS/) {
-        push @requires, "bdftopcf", "mkfontdir";
+        push @requires, "bdftopcf", "mkfontscale";
         $isFont = 1;
     }
 
     if ($file =~ /XORG_FONT_SCALED_UTILS/) {
-        push @requires, "mkfontscale", "mkfontdir";
+        push @requires, "mkfontscale";
         $isFont = 1;
     }
 

pkgs/servers/x11/xorg/overrides.nix

@@ -75,8 +75,10 @@ self: super:
     inherit tradcpp;
   });
 
-  mkfontdir = super.mkfontdir.overrideAttrs (attrs: {
-    preBuild = "substituteInPlace mkfontdir.in --replace @bindir@ ${self.mkfontscale}/bin";
+  mkfontdir = self.mkfontscale;
+
+  mkfontscale = super.mkfontscale.overrideAttrs (attrs: {
+    preBuild = "substituteInPlace mkfontdir.in --replace @bindir@ ${placeholder "out"}/bin";
   });
 
   libxcb = super.libxcb.overrideAttrs (attrs: {