meson: disable bootctl without libblkid

bootctl uses blkid probe functions to find the ESP, hence it's useless without
it. Don't even try to build it if libblkid is unavailable.

meson.build

@@ -1306,7 +1306,7 @@ if conf.get('HAVE_PAM', 0) == 1
              install_dir : rootlibexecdir)
 endif
 
-if conf.get('ENABLE_EFI', 0) == 1
+if conf.get('ENABLE_EFI', 0) == 1 and conf.get('HAVE_BLKID', 0) == 1
   executable('bootctl',
              'src/boot/bootctl.c',
              include_directories : includes,

meson_options.txt

@@ -36,7 +36,7 @@ option('ldconfig', type : 'boolean',
 option('resolve', type : 'boolean',
        description : 'systemd-resolved stack')
 option('efi', type : 'boolean',
-       description : 'support for EFI')
+       description : 'enable systemd-boot and bootctl')
 option('environment-d', type : 'boolean',
        description : 'support for environment.d')
 option('binfmt', type : 'boolean',