This was disabled due to:
```
Unable to decode the command from the command line:
UnicodeEncodeError: 'utf-8' codec can't encode characters in position 13-20: surrogates not allowed
```
Note that this error isn't in `line-directive`, but in Python decoding
surrogates from the command line. Not sure why that's not allowed, but
printing from within a script works so change to that.
We already set `PYTHONIOENCODING=UTF8` in the environment in
`test/lit.cfg`, which makes sure stdout is UTF8 as opposed to ASCII.
Resolves rdar://92613094.
The characters used before were in the private-use section had surrogate
chars. This led to issues with some python utf8 decoder implementations
resulting in the error
```
UnicodeEncodeError: 'utf-8' codec can't encode characters in position
13-20: surrogates not allowed
```
This uses more normal utf8 characters that should hopefully work
everywhere while still exhibiting issues decoding to ascii.
`utils/line-directive` is used when building Swift (see
`cmake/modules/AddSwift.cmake`), and includes some doctests. In order
to make sure it continues to behave as intended, add its tests to
`validation-test`.
