libid3tag: Split into multiple outputs

pkgs/development/libraries/libid3tag/default.nix

@@ -1,24 +1,33 @@
 {stdenv, fetchurl, writeText, zlib, gperf}:
 
 stdenv.mkDerivation rec {
-  version = "0.15.1b";
-
   name = "libid3tag-${version}";
+  version = "0.15.1b";
 
   src = fetchurl {
     url = mirror://sourceforge/mad/libid3tag-0.15.1b.tar.gz;
     sha256 = "63da4f6e7997278f8a3fef4c6a372d342f705051d1eeb6a46a86b03610e26151";
   };
 
+  outputs = [ "out" "dev" ];
+  setOutputFlags = false;
+
   propagatedBuildInputs = [ zlib gperf ];
 
   patches = [ ./debian-patches.patch ];
 
+  preConfigure = ''
+    configureFlagsArray+=(
+      --includedir=$dev/include
+    )
+  '';
+
   postInstall = ''
-    mkdir -p $out/lib/pkgconfig
-    cp ${./id3tag.pc} $out/lib/pkgconfig/id3tag.pc
-    substituteInPlace $out/lib/pkgconfig/id3tag.pc \
+    mkdir -p $dev/lib/pkgconfig
+    cp ${./id3tag.pc} $dev/lib/pkgconfig/id3tag.pc
+    substituteInPlace $dev/lib/pkgconfig/id3tag.pc \
       --subst-var-by out $out \
+      --subst-var-by dev $dev \
       --subst-var-by version "${version}"
   '';
 

pkgs/development/libraries/libid3tag/id3tag.pc

@@ -1,7 +1,7 @@
 prefix=@out@
 exec_prefix=${prefix}
 libdir=${exec_prefix}/lib
-includedir=${exec_prefix}/include
+includedir=@dev@/include
 
 Name: libid3tag
 Description: ID3 tag manipulation library