configure: Remove debug message

When using configure arguments like -system-libpng then we saw lines
like this in configure's output:

opt: libpng val: system

This is a left-over debug message which went unnoticed for a long time.
This patch removes it.

Change-Id: Ic655fbc9aedb887743206fdfb344bf2f5eca7a12
Reviewed-by:  Alexey Edelev <alexey.edelev@qt.io>

cmake/QtProcessConfigureArgs.cmake

@@ -684,7 +684,6 @@ while(1)
         if(NOT DEFINED commandline_option_${opt} AND opt MATCHES "(qt|system)-(.*)")
             set(opt "${CMAKE_MATCH_2}")
             set(val "${CMAKE_MATCH_1}")
-            message("opt: ${opt} val: ${val}")
         endif()
     else()
         qtConfAddError("Invalid command line parameter '${arg}'.")