xorg-server: fixed compiler flags injection when X11R6 flag is set which failed on "pure" 64 bit targets

xorg/xorg-server/parse-config

@@ -14,10 +14,10 @@
 # --- SDE-COPYRIGHT-NOTE-END ---
 
 if hasflag X11R6; then
-	var_append CPP_WRAPPER_INSERT ' ' '*/X11R6/include?-I/usr/X11/include'
-	var_append GCC_WRAPPER_INSERT ' ' '*/X11R6/include?-I/usr/X11/include'
-	var_append GCC_WRAPPER_INSERT ' ' '*/X11R6/lib?-L/usr/X11/lib'
-	var_append GCC_WRAPPER_INSERT ' ' '*/X11R6/lib64?-L/usr/X11/lib64'
+	var_append CPP_WRAPPER_INSERT ' ' '*/X11R6/include?-I'"$(pkgprefix -r includedir libx11)"
+	var_append GCC_WRAPPER_INSERT ' ' '*/X11R6/include?-I'"$(pkgprefix -r includedir libx11)"
+	var_append GCC_WRAPPER_INSERT ' ' '*/X11R6/lib?-L'"$(pkgprefix -r libdir libx11)"
+	var_append GCC_WRAPPER_INSERT ' ' '*/X11R6/lib64?-L'"$(pkgprefix -r libdir libx11)"
 fi
 
 if atstage cross && pkginstalled -f libx11; then