QA: Only build kicad2step tests if the lib exists

If neither OCC or OCE is available, the kicad2step_lib
target is not created, so the unit tests also cannot
be built. Detect missing libs and abort the test
target creation in that case.

Reverts (and fixes): 3a8ffd66c

qa/CMakeLists.txt

@@ -46,7 +46,7 @@ add_subdirectory( pcbnew )
 add_subdirectory( eeschema )
 
 add_subdirectory( libs )
-# add_subdirectory( utils/kicad2step )
+add_subdirectory( utils/kicad2step )
 
 # Utility/debugging/profiling programs
 add_subdirectory( common_tools )

qa/utils/kicad2step/CMakeLists.txt

@@ -21,6 +21,11 @@
 
 # kicad2step s-expr handling routines
 
+if( NOT TARGET kicad2step_lib )
+    # Can't build this test without the underlying library
+    return()
+endif()
+
 set( K2S_TEST_SRCS
     test_module.cpp