build: better handle non-guile build

meson.build

@@ -312,7 +312,7 @@ if not get_option('scm').disabled() and guile_dep.found()
   subdir('scm')
 else
   # dummy-dep.
-  mu_scm_dep = declare_dependency('', required:false)
+  mu_scm_dep = declare_dependency()
 endif
 
 subdir('mu')

mu/mu-cmd.cc

@@ -35,9 +35,9 @@
 #include "message/mu-message.hh"
 #include "message/mu-mime-object.hh"
 
-#if BUILD_GUILE
+#if BUILD_GUILE || BUILD_SCM
 #include "scm/mu-scm.hh"
-#endif/*BUILD_GUILE*/
+#endif/*BUILD_GUILE || BUILD_SCM*/
 
 #include "utils/mu-error.hh"
 #include "utils/mu-utils-file.hh"