build: tools: use absolute path in LDADD
build: tools: use absolute path in LDADD

Specify the path to libgpiod starting from the top project directory.

Signed-off-by: Bartosz Golaszewski <108de5fbc428215dc26df4468b48691526611148@gmail.com>

brgl/libgpiod,brgl/libgpiod,brgl/libgpiod,brgl/libgpiod