meson: Properly check dependencies of mkosi target

Let's insist on mkosi being found if the integration-tests option
is enabled and let's only add dependencies on systemd-journal-remote
and systemd-measure if they're being built. Drop ukify from the list
as its part of public_programs.

Author: DaanDeMeyer

meson.build

@@ -321,6 +321,7 @@ meson_build_sh = find_program('tools/meson-build.sh')
 want_tests = get_option('tests')
 slow_tests = want_tests != 'false' and get_option('slow-tests')
 fuzz_tests = want_tests != 'false' and get_option('fuzz-tests')
+integration_tests = want_tests != 'false' and get_option('integration-tests')
 install_tests = want_tests != 'false' and get_option('install-tests')
 
 if add_languages('cpp', native : false, required : fuzzer_build)
@@ -2574,6 +2575,18 @@ endif
 #####################################################################
 
 mkosi = find_program('mkosi', required : false)
+if integration_tests and not mkosi.found()
+        error('Could not find mkosi which is required to run the integration tests')
+endif
+
+mkosi_depends = public_programs
+
+foreach executable : ['systemd-journal-remote', 'systemd-measure']
+        if executable in executables_by_name
+                mkosi_depends += [executables_by_name[executable]]
+        endif
+endforeach
+
 if mkosi.found()
         custom_target('mkosi',
                 build_always_stale : true,
@@ -2588,13 +2601,9 @@ if mkosi.found()
                         '--build-dir', meson.current_build_dir() / 'mkosi.builddir',
                         '--force',
                         '--debug',
-                        'build'
-                ],
-                depends : public_programs + [
-                        executables_by_name['systemd-journal-remote'],
-                        executables_by_name['systemd-measure'],
-                        ukify,
+                        'build',
                 ],
+                depends : mkosi_depends,
         )
 endif