Add a few more bypass environment variables

When we're building ParticleOS images, we don't want the package
manager (or mkosi) to run systemd-sysusers, systemd-tmpfiles or
systemctl preset so let's add a few more bypass environment
variables that we can set to have execution of these skipped like
we already have $SYSTEMD_HWDB_UPDATE_BYPASS and $KERNEL_INSTALL_BYPASS.

src/systemctl/systemctl-enable.c

@@ -9,6 +9,7 @@
 #include "systemctl-sysv-compat.h"
 #include "systemctl-util.h"
 #include "systemctl.h"
+#include "verbs.h"
 
 static int normalize_link_paths(char **paths) {
         int r;
@@ -75,6 +76,9 @@ int verb_enable(int argc, char *argv[], void *userdata) {
         sd_bus *bus = NULL;
         int r;
 
+        if (streq(verb, "preset") && should_bypass("SYSTEMD_PRESET"))
+                return 0;
+
         const char *operation = strjoina("to ", verb);
         r = mangle_names(operation, ASSERT_PTR(strv_skip(argv, 1)), &names);
         if (r < 0)

src/systemctl/systemctl-preset-all.c

@@ -6,10 +6,14 @@
 #include "systemctl-preset-all.h"
 #include "systemctl-util.h"
 #include "systemctl.h"
+#include "verbs.h"
 
 int verb_preset_all(int argc, char *argv[], void *userdata) {
         int r;
 
+        if (should_bypass("SYSTEMD_PRESET"))
+                return 0;
+
         if (install_client_side()) {
                 InstallChange *changes = NULL;
                 size_t n_changes = 0;