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='2020-11-28 19:51:40 +0100'>2020-11-28</span></td><td><a href='/guix/commit/gnu/tests/databases.scm?id=97c4fd21bdd7470da91c4a47aab1d6357bdc8080'>services: MySQL: Add more tests.</a><span class='msg-avail'>...</span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2020-11-28 19:51:40 +0100'>2020-11-28</span></td><td><a href='/guix/commit/gnu/tests/databases.scm?id=e20388ad7f94e72a7a71272a742031fb5c1fbb4b'>services: MySQL: Upgrade database schemas automatically.</a><span class='msg-avail'>...</span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2020-11-28 19:51:40 +0100'>2020-11-28</span></td><td><a href='/guix/commit/gnu/tests/databases.scm?id=89b704a456ef1cdef855a6c483832a05e1117f24'>services: MySQL: Deprecate 'mysql-service'.</a><span class='msg-avail'>...</span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2020-10-20 22:39:43 +0100'>2020-10-20</span></td><td><a href='/guix/commit/gnu/tests/databases.scm?id=bdcf4d88d58798eca7811c8b1fbd4638168d05c3'>services: databases: Don't specify a default postgresql version.</a><span class='msg-avail'>...</span></td><td>Christopher Baines</td></tr>