extract: Allow p11_save_write() to automatically calculate length

Also if automatically calculating length, then ignore input
that is NULL, as something that shouldn't be written out.

This allows easier chaining of optional output, such as comments.

https://bugs.freedesktop.org/show_bug.cgi?id=62029

1 files changed, 0 insertions, 0 deletions

diff --git a/tools/tests/files/empty-file b/tools/tests/files/empty-file
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/tools/tests/files/empty-file