Fix -hostprefix behaviour

When -hostprefix ./configure option is used, Qt installs all its
headers, libraries and binaries inside the given host prefix, instead
of the prefix. This is used by Buildroot to make sure that all Qt
libraries and headers are installed in $(STAGING_DIR).

Qt ./configure script also allows to tune the installation location of
various elements, for examples the plugins through the -plugindir
option. Unfortunately, this option only impact the installation path
on the target, but not on the host when -hostprefix is used.

This patch modifies Qt ./configure script so that HOST_*PATH_STR
variables are composed of the host prefix concatenated with the path
of installation on the target. This way, the plugin installation local
in the $(STAGING_DIR) and on the target remains the same.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

Index: qt-4.7.2/configure
===================================================================
--- qt-4.7.2.orig/configure	2011-03-31 22:28:16.530647168 +0200
+++ qt-4.7.2/configure	2011-03-31 22:29:38.908081695 +0200
@@ -4456,15 +4456,15 @@


 if [ ! -z "$QT_HOST_PREFIX" ]; then
-    HOSTPREFIX_PATH_STR=`"$relpath/config.tests/unix/padstring" 268 "qt_prfxpath=$QT_HOST_PREFIX"`
-    HOSTDOCUMENTATION_PATH_STR=`"$relpath/config.tests/unix/padstring" 268 "qt_docspath=$QT_HOST_PREFIX/doc"`
-    HOSTHEADERS_PATH_STR=`"$relpath/config.tests/unix/padstring" 268 "qt_hdrspath=$QT_HOST_PREFIX/include"`
-    HOSTLIBRARIES_PATH_STR=`"$relpath/config.tests/unix/padstring" 268 "qt_libspath=$QT_HOST_PREFIX/lib"`
-    HOSTBINARIES_PATH_STR=`"$relpath/config.tests/unix/padstring" 268 "qt_binspath=$QT_HOST_PREFIX/bin"`
-    HOSTPLUGINS_PATH_STR=`"$relpath/config.tests/unix/padstring" 268 "qt_plugpath=$QT_HOST_PREFIX/plugins"`
-    HOSTIMPORTS_PATH_STR=`"$relpath/config.tests/unix/padstring" 268 "qt_impspath=$QT_HOST_PREFIX/IMPORTS"`
-    HOSTDATA_PATH_STR=`"$relpath/config.tests/unix/padstring" 268 "qt_datapath=$QT_HOST_PREFIX"`
-    HOSTTRANSLATIONS_PATH_STR=`"$relpath/config.tests/unix/padstring" 268 "qt_trnspath=$QT_HOST_PREFIX/translations"`
+    HOSTPREFIX_PATH_STR=`"$relpath/config.tests/unix/padstring" 268 "qt_prfxpath=$QT_HOST_PREFIX/$QT_INSTALL_PREFIX"`
+    HOSTDOCUMENTATION_PATH_STR=`"$relpath/config.tests/unix/padstring" 268 "qt_docspath=$QT_HOST_PREFIX/$QT_INSTALL_DOCS"`
+    HOSTHEADERS_PATH_STR=`"$relpath/config.tests/unix/padstring" 268 "qt_hdrspath=$QT_HOST_PREFIX/$QT_INSTALL_HEADERS"`
+    HOSTLIBRARIES_PATH_STR=`"$relpath/config.tests/unix/padstring" 268 "qt_libspath=$QT_HOST_PREFIX/$QT_INSTALL_LIBS"`
+    HOSTBINARIES_PATH_STR=`"$relpath/config.tests/unix/padstring" 268 "qt_binspath=$QT_HOST_PREFIX/$QT_INSTALL_BINS"`
+    HOSTPLUGINS_PATH_STR=`"$relpath/config.tests/unix/padstring" 268 "qt_plugpath=$QT_HOST_PREFIX/$QT_INSTALL_PLUGINS"`
+    HOSTIMPORTS_PATH_STR=`"$relpath/config.tests/unix/padstring" 268 "qt_impspath=$QT_HOST_PREFIX/$QT_INSTALL_IMPORTS"`
+    HOSTDATA_PATH_STR=`"$relpath/config.tests/unix/padstring" 268 "qt_datapath=$QT_HOST_PREFIX/$QT_INSTALL_DATA"`
+    HOSTTRANSLATIONS_PATH_STR=`"$relpath/config.tests/unix/padstring" 268 "qt_trnspath=$QT_HOST_PREFIX/$QT_INSTALL_TRANSLATIONS"`
     HOSTSETTINGS_PATH_STR=`"$relpath/config.tests/unix/padstring" 268 "qt_stngpath=$QT_INSTALL_SETTINGS"`
     HOSTEXAMPLES_PATH_STR=`"$relpath/config.tests/unix/padstring" 268 "qt_xmplpath=$QT_INSTALL_EXAMPLES"`
     HOSTDEMOS_PATH_STR=`"$relpath/config.tests/unix/padstring" 268 "qt_demopath=$QT_INSTALL_DEMOS"`