Add QT5_CUSTOM_DIR as Qt root dir for install and lib subdirs

configure.in

@@ -3361,12 +3361,24 @@ libraries returned by 'pkg-config gtk+-2.0 --libs' or 'gtk-config
 
 
     if test "$wxUSE_QT" = 1; then
-        PKG_CHECK_MODULES(QT5,
+        TOOLKIT=QT
+        GUIDIST=QT_DIST
+        TOOLKIT_DIR="qt"
+
+        if test -n "$QT5_CUSTOM_DIR" ; then
+            dnl the name of the directory where the files for this toolkit live
+            TOOLKIT_INCLUDE="${TOOLKIT_INCLUDE} -I${QT5_CUSTOM_DIR}/include"
+            GUI_TK_LIBRARY="${GUI_TK_LIBRARY} -L${QT5_CUSTOM_DIR}/lib \
+                            -lQt5Core -lQt5Widgets -lQt5Gui -lQt5OpenGL -lQt5Test \
+                            -Wl,-rpath,${QT5_CUSTOM_DIR}/lib"
+
+        elif test -z "$PKG_CONFIG" ; then
+            AC_MSG_ERROR([specify QT5_CUSTOM_DIR or make sure pkg-config is available to search for Qt5 libraries])
+
+        else
+            PKG_CHECK_MODULES(QT5,
                           [Qt5Core Qt5Widgets Qt5Gui Qt5OpenGL Qt5Test],
-            [
-                TOOLKIT=QT
-                GUIDIST=QT_DIST
-                TOOLKIT_DIR="qt"
+                [
                 TOOLKIT_INCLUDE="${TOOLKIT_INCLUDE} ${QT5_CFLAGS}"
                 GUI_TK_LIBRARY="${GUI_TK_LIBRARY} ${QT5_LIBS}"
                 if `pkg-config --variable qt_config Qt5Core | grep "reduce_relocations" >/dev/null`; then
@@ -3374,11 +3386,12 @@ libraries returned by 'pkg-config gtk+-2.0 --libs' or 'gtk-config
                     SAMPLES_CXXFLAGS="-fPIC $SAMPLES_CXXFLAGS"
                     WXCONFIG_CXXFLAGS="-fPIC $WXCONFIG_CXXFLAGS"
                 fi
-            ],
-            [
-                AC_MSG_ERROR([Qt5 libraries are not available])
-            ]
-        )
+                ],
+                [
+                    AC_MSG_ERROR([Qt5 libraries are not available])
+                ]
+            )
+        fi
     fi
     dnl the name of the directory where the files for this toolkit live
     TOOLKIT_DIR=`echo ${TOOLKIT} | tr '[[A-Z]]' '[[a-z]]'`