package/systemd: add optional tpm2 dependency

When tpm2-tss package is selected, systemd can enable its TPM2 support
[1] used by systemd-boot, systemd-cryptenroll (when cryptsetup package
is also enabled) [2] and other tool systemd-pcr{extend,lock,machine}.

[1] https://github.com/systemd/systemd/blob/db11bab38ccf1ed257f310d29070843d4c58ea01/meson.build#L1341
[2] https://www.freedesktop.org/software/systemd/man/latest/systemd-cryptenroll.html

Signed-off-by: Romain Naour <romain.naour@smile.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/systemd/systemd.mk

@@ -577,6 +577,13 @@ else
 SYSTEMD_CONF_OPTS += -Dhibernate=false
 endif
 
+ifeq ($(BR2_PACKAGE_TPM2_TSS),y)
+SYSTEMD_DEPENDENCIES += tpm2-tss
+SYSTEMD_CONF_OPTS += -Dtpm2=true
+else
+SYSTEMD_CONF_OPTS += -Dtpm2=false
+endif
+
 ifeq ($(BR2_PACKAGE_SYSTEMD_BOOT),y)
 SYSTEMD_INSTALL_IMAGES = YES
 SYSTEMD_DEPENDENCIES += gnu-efi host-python-pyelftools