Fix OrcaSlicer_profile_validator link error with undefined nsvg symbols

When ORCA_TOOLS is enabled, the profile_validator target links libslic3r
which uses nsvg functions, but no translation unit in its link set defines
NANOSVG_IMPLEMENTATION. Add it to the validator source file.

src/dev-utils/OrcaSlicer_profile_validator.cpp

@@ -1,3 +1,5 @@
+#define NANOSVG_IMPLEMENTATION
+#include "nanosvg/nanosvg.h"
 #include "libslic3r/GCode.hpp"
 #include "libslic3r/Preset.hpp"
 #include "libslic3r/Config.hpp"