dont mindlessly touch the icc-header file on every build

- this little gremlin touches the header file everytime it is run
- as icc is very low level, this causes a lot of pointless rebuild
- everything from vcl up gets relinked
- this slows every empty 'make build' down by more than 40 percent
- would really need to check if the file changed before writing, but as we
  rarely change icc itself, I didnt bother with that

icc/source/create_sRGB_profile/create_sRGB_profile.cpp

@@ -474,6 +474,11 @@ int main(int argc, char* argv[])
         profile.Write(&out);
         out.Close();
 
+        if(FILE *headerfile_exists = fopen(hxx_file_name,"r"))
+        {
+            fclose(headerfile_exists);
+            exit(0);
+        }
         FILE *headerfile = fopen(hxx_file_name,"w");
 
         //print OpenOffice standard file header