[libmediaart] build: Allow Qt4 or Qt5 to be forced

[Martyn James Russell <mr src gnome org>]

commit 67aae986ac2dc5ae4a4d5adcc747f00e77b79199
Author: Paweł Stankowski <ak_ambi op pl>
Date:   Sun May 31 13:50:53 2015 +0100

    build: Allow Qt4 or Qt5 to be forced
    
    Adds optional configure flag "--with-qt-version=<4|5>" that may be used to
    enforce qt 4.x or qt 5.x version.

 configure.ac |   25 +++++++++++++++++--------
 1 files changed, 17 insertions(+), 8 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index e9ead09..b347490 100644
--- a/configure.ac
+++ b/configure.ac
@@ -207,6 +207,11 @@ AC_ARG_ENABLE(qt,
                              [enable Qt support, (MP3 album art) [[default=auto]]]),,
               [enable_qt=auto])
 
+AC_ARG_WITH(qt-version,
+            AS_HELP_STRING([--with-qt-version=major],
+                           [Force specific Qt version [[default=auto]]]),,
+            [with_qt_version=auto])
+
 selected_for_media_art="no  (disabled)"
 
 ##################################################################
@@ -218,14 +223,18 @@ if test "x$enable_qt" == "xyes" && test "x$enable_gdkpixbuf" == "xyes"; then
 fi
 
 if test "x$enable_qt" != "xno" && test "x$enable_gdkpixbuf" != "xyes"; then
-   PKG_CHECK_MODULES(QT5,
-                     [Qt5Gui >= $QT5_REQUIRED],
-                     [have_qt5=yes],
-                     [have_qt5=no])
-   PKG_CHECK_MODULES(QT4,
-                     [QtGui >= $QT4_REQUIRED],
-                     [have_qt4=yes],
-                     [have_qt4=no])
+   if test "x$with_qt_version" == "xauto" || test "x$with_qt_version" == "x5"; then
+       PKG_CHECK_MODULES(QT5,
+                         [Qt5Gui >= $QT5_REQUIRED],
+                         [have_qt5=yes],
+                         [have_qt5=no])
+   fi
+   if test "x$with_qt_version" == "xauto" || test "x$with_qt_version" == "x4"; then
+       PKG_CHECK_MODULES(QT4,
+                         [QtGui >= $QT4_REQUIRED],
+                         [have_qt4=yes],
+                         [have_qt4=no])
+   fi
 
    if test "x$have_qt5" = "xyes"; then
       BACKEND_CFLAGS="$QT5_CFLAGS -fPIC"