Normalize line endings in SkSL error tests
Normalize line endings in SkSL error tests

On Windows, the process output contains CRLF sequences. Calling
splitlines() recognizes those (Python universal line endings), so we get
a list of the output lines. Joining those with '\n' produces a string
that just has LF. (We add another one, so we still end the file with a
newline). Because we've opened the file in binary mode, the resulting
files now look the same, regardless of OS.

Change-Id: I1f032aa6e0f82057f593c25ce0676983733b9e56
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/317105
Reviewed-by: John Stiles <f4fcf42d3bb5924557f1eeb3be66747535e585da@google.com>
Commit-Queue: Brian Osman <794c0b5534edf5601d88e1d41975d0262da12894@google.com>

aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,google/skia,google/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,google/skia