rpm: fix issues when running on old linux

When running on CentOS7 I was getting some weird encoding issues,
mostly because it was falling back to ascii encoding by default:
```
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 1045: ordinal not in range(128)
```

By passing utf-8 directly it seems to solve part of the issues

pkg/make_rpm.py

@@ -109,7 +109,7 @@ def CopyAndRewrite(input_file, output_file, replacements=None, template_replacem
   """
 
   with open(output_file, 'w') as output:
-    for line in fileinput.input(input_file):
+    for line in fileinput.input(input_file, encoding='utf-8'):
       if replacements:
         for prefix, text in replacements.items():
           if line.startswith(prefix):