[antlir] Add mkfs.ext4 options to improve build speed

Summary:
Playing around with options that should theoretically improve the build creation time for CVM builds. This is on the critical path and I want to make sure that these options are applied, but also safely applied.

I'm going to make sure that CVM builds are triggered on the `ext4` packager, since we are the primary and only customer for this anyways.

Test Plan: Wait for CVM cogwheel tests to all go green. Then, in a few days, check the build graphs to see if we notice an improvement in build times.

Reviewed By: vmagro

Differential Revision: D86312712

fbshipit-source-id: 3583715f5dfd17191edb34bc0a080a5a6683e71e

Author: CookieComputing

antlir/antlir2/antlir2_packager/src/ext4.rs

@@ -58,6 +58,11 @@ impl PackageFormat for Ext4 {
         }
         cmd.arg("-d").arg("/__antlir2__/root");
         cmd.arg(MAPPED_OUTPUT);
+        cmd.arg("-O");
+        // Features derived from https://linux.die.net/man/8/mkfs.ext4
+        cmd.arg("dir_index,extent,large_file,sparse_super,uninit_bg");
+        cmd.arg("-E");
+        cmd.arg("discard,lazy_itable_init=1,lazy_journal_init=1");
         if let Some(size_mb) = self.size_mb {
             cmd.arg(format!("{}M", size_mb));
             run_cmd(&mut cmd).context("failed to build ext4 archive")?;