boot: Add EFISTUB and refactor boot protocols

meson.build

@@ -2,7 +2,7 @@ project(
     'zinnia',
     license: 'ISC',
     version: '0.1.0',
-    meson_version: '>=1.5.0',
+    meson_version: '>=1.6.0',
     default_options: [
         'c_std=gnu23',
         'werror=true',
@@ -95,7 +95,6 @@ modules = {}
 
 # These dirs go first so we can add arch-specific flags to drivers.
 subdir('arch' / target_machine.cpu_family())
-subdir('boot')
 subdir('lib')
 subdir('mem')
 subdir('sched')
@@ -175,6 +174,8 @@ kernel = executable(
     install_dir: zinnia_datadir,
 )
 
+subdir('boot')
+
 foreach name, v : modular_modules
     shared_library(
         name,