fdkaacenc: check fdk-aac version in meson.build

configure.ac used to set -DHAVE_FDK_AAC_0_1_4 , which enables
7.1 support.

https://bugzilla.gnome.org/show_bug.cgi?id=789471

ext/fdkaac/meson.build

@@ -1,9 +1,16 @@
 fdkaac_dep = dependency('fdk-aac', required : false)
 
 if fdkaac_dep.found()
+  fdkaac_defines = []
+
+  # Enable 7.1 support
+  if fdkaac_dep.version().version_compare('>=0.1.4')
+    fdkaac_defines += ['-DHAVE_FDK_AAC_0_1_4']
+  endif
+
   gstfdkaac = library('gstfdkaac',
     ['plugin.c', 'gstfdkaacenc.c', 'gstfdkaacdec.c'],
-    c_args : gst_plugins_bad_args,
+    c_args : gst_plugins_bad_args + fdkaac_defines,
     include_directories : [configinc],
     dependencies : [gstaudio_dep, gstpbutils_dep, fdkaac_dep],
     install : true,