Tests/BuildDepends: Make 3-second delay more robust

Use "cmake -E sleep 3" instead of execute_process with a TIMEOUT of 3.
This avoids using a busy loop or depending on a timeout to kill it.

Tests/BuildDepends/CMakeLists.txt

@@ -182,8 +182,7 @@ else()
 endif()
 
 message("Waiting 3 seconds...")
-# any additional argument will cause ${bar} to wait forever
-execute_process(COMMAND ${bar} -infinite TIMEOUT 3 OUTPUT_VARIABLE out)
+execute_process(COMMAND ${CMAKE_COMMAND} -E sleep 3)
 
 message("Modifying Project/foo.cxx")
 write_file(${BuildDepends_BINARY_DIR}/Project/foo.cxx

Tests/BuildDepends/Project/bar.cxx

@@ -15,11 +15,5 @@ int main(int argc, char** argv)
   /* Print out the string that should have been regenerated.  */
   printf("%s\n", regen_string);
   fflush(stdout);
-  // if any argument is used, wait forever
-  if (argc>1)
-    {
-    // wait that we get killed...
-    for(;;);
-    }
   return 0;
 }