configure: add '-psql_config' option

Allow setting of pg_config path for cross compilation where pg_config is
not in the command search path (do the same as for mysql_config).
This is e.g. used for buildroot (see [1] for details).

[1] http://lists.busybox.net/pipermail/buildroot/2015-February/119714.html

Change-Id: I11d084496ffbb6f8bc350dbcf2971a5be8e3b346
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>

configure

@@ -578,6 +578,7 @@ CFG_WIDGETS=yes
 CFG_QCONFIG=full
 CFG_DEBUG=auto
 CFG_MYSQL_CONFIG=
+CFG_PSQL_CONFIG=
 CFG_DEBUG_RELEASE=no
 CFG_FORCEDEBUGINFO=no
 CFG_SHARED=yes
@@ -885,6 +886,7 @@ while [ "$#" -gt 0 ]; do
     -arch| \
     -host-arch| \
     -mysql_config| \
+    -psql_config| \
     -qpa| \
     -qconfig| \
     -qreal| \
@@ -1066,6 +1068,9 @@ while [ "$#" -gt 0 ]; do
     mysql_config)
 	CFG_MYSQL_CONFIG="$VAL"
 	;;
+    psql_config)
+        CFG_PSQL_CONFIG="$VAL"
+        ;;
     prefix)
         QT_INSTALL_PREFIX="$VAL"
         ;;
@@ -4386,10 +4391,11 @@ for _SQLDR in $CFG_SQL_AVAILABLE; do
             ;;
         psql)
             if [ "$CFG_SQL_psql" != "no" ]; then
+                [ -z "$CFG_PSQL_CONFIG" ] && CFG_PSQL_CONFIG=`"$WHICH" pg_config`
                 # Be careful not to use native pg_config when cross building.
-                if [ "$XPLATFORM_MINGW" != "yes" ] && "$WHICH" pg_config >/dev/null 2>&1; then
-                    QT_CFLAGS_PSQL=`pg_config --includedir 2>/dev/null | filterIncludePath`
-                    QT_LFLAGS_PSQL=`pg_config --libdir 2>/dev/null | filterLibraryPath`
+                if [ "$XPLATFORM_MINGW" != "yes" ] && [ -x "$CFG_PSQL_CONFIG" ]; then
+                    QT_CFLAGS_PSQL=`$CFG_PSQL_CONFIG --includedir 2>/dev/null | filterIncludePath`
+                    QT_LFLAGS_PSQL=`$CFG_PSQL_CONFIG --libdir 2>/dev/null | filterLibraryPath`
                 fi
                 [ -z "$QT_CFLAGS_PSQL" ] || QT_CFLAGS_PSQL="-I$QT_CFLAGS_PSQL"
                 [ -z "$QT_LFLAGS_PSQL" ] || QT_LFLAGS_PSQL="-L$QT_LFLAGS_PSQL"