- Recognise OpenBSD, reuse FreeBSD sources

Index: libfwupdplugin/meson.build
--- libfwupdplugin/meson.build.orig
+++ libfwupdplugin/meson.build
@@ -158,7 +158,7 @@ fwupdplugin_src = [
 if host_machine.system() == 'linux'
   fwupdplugin_src += 'fu-common-linux.c' # fuzzing
   fwupdplugin_src += 'fu-efivar-linux.c'
-elif host_machine.system() == 'freebsd'
+elif host_machine.system() in ['freebsd', 'openbsd']
   fwupdplugin_src += 'fu-common-freebsd.c'
   fwupdplugin_src += 'fu-efivar-freebsd.c'
 elif host_machine.system() == 'windows'
