[LyX/2.3-staging] Do not search for X in mingw builds

[Georg Baum]

commit eb8d69e2320bfb6004d13a479d2794dfa5cca031
Author: Georg Baum <b...@lyx.org>
Date:   Thu May 5 12:41:24 2016 +0200

    Do not search for X in mingw builds
    
    The manual qt configuration did not work previously for mingw builds, since 
it
    serached for X libraries, which are not used by LyX on mingw.

diff --git a/config/qt4.m4 b/config/qt4.m4
index 33029b9..2bcd4f3 100644
--- a/config/qt4.m4
+++ b/config/qt4.m4
@@ -253,8 +253,13 @@ AC_DEFUN([QT_DO_PKG_CONFIG],
 AC_DEFUN([QT_DO_MANUAL_CONFIG],
 [
        dnl Check for X libraries
-       AC_PATH_X
-       AC_PATH_XTRA
+       case ${host} in
+       *mingw*) ;;
+       *) \
+         AC_PATH_X \
+         AC_PATH_XTRA \
+       ;;
+       esac
        case $have_x in
            yes) LIBS="$X_PRE_LIBS $LIBS $X_LIBS -lX11 $X_EXTRA_LIBS"
                 CPPFLAGS="$CPPFLAGS $X_CFLAGS";;