mdist: Filter out buildtype to avoid warning

Since we parse buildoptions.json to pass options, we end up passing
-Dbuildtype and also -Doptimization and -Ddebug which triggers the
warning:

WARNING: Recommend using either -Dbuildtype or -Doptimization + -Ddebug [...]

Filter out buildtype. It is redundant.

mesonbuild/mdist.py

@@ -213,7 +213,7 @@ def check_dist(packagename, meson_command, extra_meson_args, bld_root, privdir):
     unpacked_src_dir = unpacked_files[0]
     with open(os.path.join(bld_root, 'meson-info', 'intro-buildoptions.json')) as boptions:
         meson_command += ['-D{name}={value}'.format(**o) for o in json.load(boptions)
-                          if o['name'] not in ['backend', 'install_umask']]
+                          if o['name'] not in ['backend', 'install_umask', 'buildtype']]
     meson_command += extra_meson_args
 
     ret = run_dist_steps(meson_command, unpacked_src_dir, builddir, installdir, ninja_bin)