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='2019-01-16 16:08:22 +0100'>2019-01-16</span></td><td><a href='/guix/commit/gnu/packages/dbm.scm?id=255d1bbe777a824be726edeb9fd47458a3a877a9'>gnu: Move dbm databases to new module.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/databases.scm (gdbm, bdb, bdb-5.3): Move from here...
* gnu/packages/dbm.scm: ...to this new module.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add it.
* gnu/packages/audio.scm,
gnu/packages/avahi.scm,
gnu/packages/backup.scm,
gnu/packages/cobol.scm,
gnu/packages/cyrus-sasl.scm,
gnu/packages/databases.scm,
gnu/packages/finance.scm,
gnu/packages/game-development.scm,
gnu/packages/gnome.scm,
gnu/packages/guile.scm,
gnu/packages/ibus.scm,
gnu/packages/kerberos.scm,
gnu/packages/linux.scm,
gnu/packages/mail.scm,
gnu/packages/man.scm,
gnu/packages/nvi.scm,
gnu/packages/openldap.scm,
gnu/packages/package-management.scm,
gnu/packages/php.scm,
gnu/packages/pulseaudio.scm,
gnu/packages/python.scm,
gnu/packages/rdf.scm,
gnu/packages/ruby.scm,
gnu/packages/sawfish.scm: Update module references.
</span></span></td><td>Ricardo Wurmus</td></tr>