qt56.qtwebengine: make it build

This is an updated version of #16561 with added qt.conf to fix QtWebEngineProcess not being able to find locales

pkgs/development/libraries/qt-5/5.6/qtwebengine.nix

@@ -1,6 +1,62 @@
-{ qtSubmodule, qtquickcontrols, qtlocation, qtwebchannel }:
+{ qtSubmodule, qtquickcontrols, qtlocation, qtwebchannel
+
+, xlibs, libXcursor, libXScrnSaver, libXrandr, libXtst
+, fontconfig, freetype, harfbuzz, icu, dbus
+, zlib, libjpeg, libpng, libtiff
+, alsaLib
+, libcap
+, pciutils
+
+, bison, flex, git, which, gperf
+, coreutils
+, pkgconfig, python
+
+}:
 
 qtSubmodule {
   name = "qtwebengine";
   qtInputs = [ qtquickcontrols qtlocation qtwebchannel ];
+  buildInputs = [ bison flex git which gperf ];
+  nativeBuildInputs = [ pkgconfig python coreutils ];
+  doCheck = true;
+
+  enableParallelBuilding = true;
+
+  preConfigure = ''
+    export MAKEFLAGS=-j$NIX_BUILD_CORES
+    substituteInPlace ./src/3rdparty/chromium/build/common.gypi \
+      --replace /bin/echo ${coreutils}/bin/echo
+    substituteInPlace ./src/3rdparty/chromium/v8/build/toolchain.gypi \
+      --replace /bin/echo ${coreutils}/bin/echo
+    substituteInPlace ./src/3rdparty/chromium/v8/build/standalone.gypi \
+      --replace /bin/echo ${coreutils}/bin/echo
+      
+    configureFlags+="\
+        -plugindir $out/lib/qt5/plugins \
+        -importdir $out/lib/qt5/imports \
+        -qmldir $out/lib/qt5/qml \
+        -docdir $out/share/doc/qt5"
+  '';
+  propagatedBuildInputs = [
+    dbus zlib alsaLib
+
+    # Image formats
+    libjpeg libpng libtiff
+
+    # Text rendering
+    fontconfig freetype harfbuzz icu
+
+    # X11 libs
+    xlibs.xrandr libXScrnSaver libXcursor libXrandr xlibs.libpciaccess libXtst
+    xlibs.libXcomposite
+
+    libcap
+    pciutils
+  ];
+  postInstall = ''
+    cat > $out/libexec/qt.conf <<EOF
+    [Paths]
+    Prefix = ..
+    EOF
+  '';
 }