Disable reading SystemdOptions EFI Var when in SecureBoot mode

In SecureBoot mode this is probably not what you want. As your cmdline
is cryptographically signed like when using Type #2 EFI Unified Kernel
Images (https://systemd.io/BOOT_LOADER_SPECIFICATION/) The user's
intention is then that the cmdline should not be modified.  You want to
make sure that the system starts up as exactly specified in the signed
artifact.

src/shared/efi-loader.c

@@ -63,40 +63,6 @@ struct device_path device_path__contents;
 struct device_path__packed device_path__contents _packed_;
 assert_cc(sizeof(struct device_path) == sizeof(struct device_path__packed));
 
-bool is_efi_boot(void) {
-        if (detect_container() > 0)
-                return false;
-
-        return access("/sys/firmware/efi/", F_OK) >= 0;
-}
-
-static int read_flag(const char *varname) {
-        _cleanup_free_ void *v = NULL;
-        uint8_t b;
-        size_t s;
-        int r;
-
-        if (!is_efi_boot()) /* If this is not an EFI boot, assume the queried flags are zero */
-                return 0;
-
-        r = efi_get_variable(EFI_VENDOR_GLOBAL, varname, NULL, &v, &s);
-        if (r < 0)
-                return r;
-
-        if (s != 1)
-                return -EINVAL;
-
-        b = *(uint8_t *)v;
-        return !!b;
-}
-
-bool is_efi_secure_boot(void) {
-        return read_flag("SecureBoot") > 0;
-}
-
-bool is_efi_secure_boot_setup_mode(void) {
-        return read_flag("SetupMode") > 0;
-}
 
 int efi_reboot_to_firmware_supported(void) {
         _cleanup_free_ void *v = NULL;

src/shared/efi-loader.h

@@ -5,9 +5,6 @@
 
 #if ENABLE_EFI
 
-bool is_efi_boot(void);
-bool is_efi_secure_boot(void);
-bool is_efi_secure_boot_setup_mode(void);
 int efi_reboot_to_firmware_supported(void);
 int efi_get_reboot_to_firmware(void);
 int efi_set_reboot_to_firmware(bool value);
@@ -28,18 +25,6 @@ int efi_loader_get_features(uint64_t *ret);
 
 #else
 
-static inline bool is_efi_boot(void) {
-        return false;
-}
-
-static inline bool is_efi_secure_boot(void) {
-        return false;
-}
-
-static inline bool is_efi_secure_boot_setup_mode(void) {
-        return false;
-}
-
 static inline int efi_reboot_to_firmware_supported(void) {
         return -EOPNOTSUPP;
 }