data-to-c.py: autodetect line endings

When GLib code is checked out with Windows line endings (happens on Windows),
data-to-c.py embedded that line endings into generated string literal. And
then they translated to double newlines in glib-compile-resources output.

clang-cl failed to compile such files because of empty lines in the middle of
multiline macros:

    #define G_MSVC_CTOR(_func,_sym_prefix) \

      static void _func(void); \

To fix the issue, enable 'universal newlines' mode when reading the input in
data-to-c.py - translate both '\n' and '\r\n' to '\n'.

Fixes https://gitlab.gnome.org/GNOME/glib/-/issues/2340

gio/data-to-c.py

@@ -1,12 +1,13 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 import sys
 
 if len(sys.argv) < 4:
     print("Usage: {0} <filename> <variable> <output>")
 
-with open(sys.argv[1], "rb") as f:
-    in_data = f.read().decode("utf-8", "backslashreplace")
+with open(sys.argv[1], "r", encoding="utf-8", errors="backslashreplace") as f:
+    in_data = f.read()
+
 b = [r"\x{:02x}".format(ord(c)) for c in in_data]
 
 out_data = 'const char {0}[] = "'.format(sys.argv[2])