Patch taken from Nix:
   https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/libraries/qt-5/5.11/qtwebkit.patch

diff --git a/Source/WebKit2/PlatformQt.cmake b/Source/WebKit2/PlatformQt.cmake
--- a/Source/WebKit2/PlatformQt.cmake
+++ b/Source/WebKit2/PlatformQt.cmake
@@ -261,6 +261,7 @@
 list(APPEND WebKit2_SYSTEM_INCLUDE_DIRECTORIES
     ${GLIB_INCLUDE_DIRS}
     ${GSTREAMER_INCLUDE_DIRS}
+    ${GSTREAMER_PBUTILS_INCLUDE_DIRS}
     ${Qt5Quick_INCLUDE_DIRS}
     ${Qt5Quick_PRIVATE_INCLUDE_DIRS}
     ${SQLITE_INCLUDE_DIR}

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<tr><td><span title='2019-04-29 12:19:03 +0200'>2019-04-29</span></td><td><a href='/guix/commit/gnu/build/file-systems.scm?id=9d3053819dfd834a1c29a03427c41d8524b8a7d5'>file-systems: Support the 'no-atime' flag.</a><span class='msg-avail'>...</span></td><td>rendaw</td></tr>
<tr><td><span title='2019-01-17 14:04:26 +0100'>2019-01-17</span></td><td><a href='/guix/commit/gnu/build/file-systems.scm?id=8ae7044f1d6a8c6a8a91ae6c032030e1affc9772'>file-systems: Add read-luks-partition-uuid.</a><span class='msg-avail'>...</span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2019-01-17 14:04:22 +0100'>2019-01-17</span></td><td><a href='/guix/commit/gnu/build/file-systems.scm?id=983abd2cf9bd419eef6b8b45d36722f1cd683b25'>file-systems: Export read-partition-label and read-partition-uuid.</a><span class='msg-avail'>...</span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2018-12-18 16:04:26 +0100'>2018-12-18</span></td><td><a href='/guix/commit/gnu/build/file-systems.scm?id=5de5f8184530fd7e0e88514ae35cb2e9305910c1'>file-systems: Have the emergency REPL output to /dev/console.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-12-18 16:04:26 +0100'>2018-12-18</span></td><td><a href='/guix/commit/gnu/build/file-systems.scm?id=6ea6e1476ff4a18d4b4b864c3065d18ed99c69af'>file-systems: Spawn a REPL only when interaction is possible.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>