initramfs: Omit more dracut modules by default

The size of the initrd is becoming an issue on existing installations
that have a small /boot partition.

See: https://github.com/fedora-silverblue/issue-tracker/issues/676

So let's drop a few dracut modules that are not using from the initrd to
save on space in /boot:

- fips & fips-crypto-policies: FIPS is not supported on Fedora
  See: https://fedoraproject.org/wiki/Changes/RemoveFipsModeSetup
  See: https://docs.fedoraproject.org/en-US/bootc/fips-crypto-policies/
- lunmask: Do not include support from booting from a LUN SAS devices as this is
  not commonly used on laptops and desktops
- memstrack: memstrack is for debug and development
- modsign: We don't include kernel module keys in the initrd
- nss-softokn: NSS is not included in the initrd

initramfs.yaml

@@ -35,3 +35,23 @@ postprocess:
     # Add support for systemd-cryptsetup and tpm2-tss LUKS locking
     add_dracutmodules+=" tpm2-tss systemd-pcrphase "
     EOF
+
+  - |
+    #!/usr/bin/env bash
+    set -xeuo pipefail
+
+    cat > /usr/lib/dracut/dracut.conf.d/20-atomic-omit.conf << 'EOF'
+    # FIPS is not supported on Fedora
+    # See: https://fedoraproject.org/wiki/Changes/RemoveFipsModeSetup
+    # See: https://docs.fedoraproject.org/en-US/bootc/fips-crypto-policies/
+    omit_dracutmodules+=" fips fips-crypto-policies "
+    # Do not include support from booting from a LUN SAS devices as this is not
+    # commonly used on laptops and desktops
+    omit_dracutmodules+=" lunmask "
+    # memstrack is for debug and development
+    omit_dracutmodules+=" memstrack "
+    # We don't include kernel module keys in the initrd
+    omit_dracutmodules+=" modsign "
+    # NSS is not included in the initrd
+    omit_dracutmodules+=" nss-softokn "
+    EOF