meson: add runutf8 env vars and meson-python.sh script

With meson we have to use both env vars and wrapper script to run python
with correct LANG settings.

run_command() and test() have 'env' attribute so we can use it, but
custom_target() doesn't support that attribute. Environment variables
cannot by configured using 'command' because meson checks if the first
item in the list is executable so we have to use a wrapper.

Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Neal Gompa <ngompa13@gmail.com>

scripts/meson-python.sh

@@ -0,0 +1,3 @@
+#!/bin/sh
+
+LC_ALL= LANG=C LC_CTYPE=en_US.UTF-8 "$@"