Fix the fix for #391300 to require only QtWebEngine 5.10, not Qt 5.10

QtWebEngine can be newer than the rest of Qt (e.g., on Fedora 27).

This fixes the version check in WebView::savePageAs to use a macro
defined in config.h.cmake based on the version of QtWebEngineWidgets
rather than relying on QT_VERSION, which is the version of QtCore.

Reviewed By: drosca
Differential Revision: https://phabricator.kde.org/D12833
CCBUG: 391300

CMakeLists.txt

@@ -85,6 +85,8 @@ if (WIN32)
     add_definitions(-D_WIN32_WINNT=${ver})
 endif()
 
+set(HAVE_QTWEBENGINE_5_10 NOT Qt5WebEngineWidgets_VERSION VERSION_LESS 5.10.0)
+
 # Mandatory: OpenSSL
 find_package(OpenSSL REQUIRED)
 

config.h.cmake

@@ -9,3 +9,6 @@
 
 /* Disable DBus support */
 #cmakedefine DISABLE_DBUS
+
+/* QtWebEngine is at least version 5.10 */
+#cmakedefine01 HAVE_QTWEBENGINE_5_10

src/lib/webengine/webview.cpp

@@ -495,7 +495,7 @@ void WebView::copyLinkToClipboard()
 
 void WebView::savePageAs()
 {
-#if QT_VERSION >= QT_VERSION_CHECK(5, 10, 0)
+#if HAVE_QTWEBENGINE_5_10
     page()->runJavaScript(QSL("document.contentType"), WebPage::SafeJsWorld, [this](const QVariant &res) {
         const QSet<QString> webPageTypes = {
             QSL("text/html"),