meson: host_system is 'ios' when building for iOS

The cross file sets this value, and we use 'ios' in Cerbero.

meson.build

@@ -332,9 +332,10 @@ cdata.set_quoted('GST_PACKAGE_ORIGIN', get_option('package-origin'))
 host_system = host_machine.system()
 if host_system == 'linux'
   cdata.set_quoted('DEFAULT_VIDEOSRC', 'v4l2src')
-elif host_system == 'darwin'
+elif ['darwin', 'ios'].contains(host_system)
   cdata.set_quoted('DEFAULT_VIDEOSRC', 'avfvideosrc')
   cdata.set_quoted('GST_EXTRA_MODULE_SUFFIX', '.dylib')
+  # Yes, we set this for iOS too. Same as Autotools.
   cdata.set('HAVE_OSX', 1)
 else
   cdata.set_quoted('DEFAULT_VIDEOSRC', 'videotestsrc')
@@ -429,10 +430,9 @@ else
   winsock2 = []
 endif
 
-if host_machine.system() == 'darwin'
+if ['darwin', 'ios'].contains(host_system)
   add_languages('objc')
-  mobilecoreservices_dep = dependency('MobileCoreServices', required : false)
-  if mobilecoreservices_dep.found()
+  if host_system == 'ios'
     cdata.set('HAVE_IOS', 1)
   endif
 

sys/applemedia/meson.build

@@ -19,7 +19,7 @@ applemedia_args = [
 
 applemedia_objc_args = []
 applemedia_option = get_option('applemedia')
-if host_system != 'darwin' or applemedia_option.disabled()
+if not ['darwin', 'ios'].contains(host_system) or applemedia_option.disabled()
   subdir_done()
 endif
 
@@ -50,7 +50,7 @@ if videotoolbox_dep.found()
     applemedia_frameworks += [videotoolbox_dep]
 endif
 
-if cdata.has('HAVE_IOS')
+if host_system == 'ios'
     applemedia_sources += [
         'iosassetsrc.m',
         'iosglmemory.c'

sys/decklink/meson.build

@@ -31,10 +31,10 @@ else
   have_pthread_h = cdata.has('HAVE_PTHREAD_H')
   if libdl.found() and have_pthread_h
     decklink_libs = [libm, libdl, dependency('threads')]
-    if host_machine.system() == 'linux'
+    if host_system == 'linux'
       decklink_sources += ['linux/DeckLinkAPIDispatch.cpp']
       build_decklink = true
-    elif host_machine.system() == 'darwin'
+    elif ['darwin', 'ios'].contains(host_system)
       decklink_sources += ['osx/DeckLinkAPIDispatch.cpp']
       decklink_ldflags = ['-Wl,-framework,CoreFoundation']
       build_decklink = true

sys/shm/meson.build

@@ -11,7 +11,7 @@ if get_option('shm').disabled()
 endif
 
 shm_deps = []
-if host_system == 'darwin' or host_system.contains('bsd')
+if ['darwin', 'ios'].contains(host_system) or host_system.endswith('bsd')
   rt_dep = []
   shm_enabled = true
 else