Correct SQLITE3SRCDIR setting.

This is how we arrange for QtWebkit to use QtBase's bundled copy of
sqlite; without it, QtWebkit will attempt to use a system-provided
library instead, and if headers are unavailable, the build will fail.

Part of issue #12467.

build.sh

@@ -125,7 +125,7 @@ echo
 
 if [[ "$QTCORE" == "bundled" ]]; then
     export QMAKE=$PWD/src/qt/qtbase/bin/qmake
-    export SQLITE3SRCDIR=$PWD/src/qt/qtbase/3rdparty/sqlite/
+    export SQLITE3SRCDIR=$PWD/src/qt/qtbase/src/3rdparty/sqlite/
     ( cd src/qt && ./preconfig.sh $QT_CFG )
 
     echo