switch to gpt partitioning

[bootimage] / vmlinuz

diff --git a/vmlinuz b/vmlinuz
new file mode 120000 (symlink)
index 0000000..327b3aa
--- /dev/null
+++ b/vmlinuz
@@ -0,0 +1 @@
+stretch_uefi_root/vmlinuz
\ No newline at end of file