read sick_scan_base_DIR from environment

etc/cmake/Findsick_scan_base.cmake

@@ -5,7 +5,12 @@
 
 include(FindPackageHandleStandardArgs)
 
-message(STATUS ${sick_scan_base_DIR})
+
+if (DEFINED ENV{sick_scan_base_DIR})
+	if(NOT DEFINED sick_scan_base_DIR)
+		set(sick_scan_base_DIR $ENV{sick_scan_base_DIR})
+	endif()
+endif()
 
 #if(NOT "$ENV{sick_scan_base_DIR}" EQUAL "")
 #    set(sick_scan_base_DIR $ENV{sick_scan_base_DIR} CACHE PATH "Path to sick_scan_base" FORCE)