[lit] Fix TestRunner unit test on Windows
Summary:
Normally Python converts all newline characters, Windows or Unix,
to Unix newlines when opening a file. However, lit opens files in
binary mode, which does not perform this conversion. As a result,
trailing Windows newlines are not stripped from test input, which
caused a failure in the TestRunner unit test:
```
FAIL: test_custom (__main__.TestIntegratedTestKeywordParser)
----------------------------------------------------------------------
Traceback (most recent call last):
File "C:\Users\bgesiak\src\llvm\llvm\utils\lit\tests\unit\TestRunner.py", line 109, in test_custom
self.assertItemsEqual(value, ['a', 'b', 'c'])
AssertionError: Element counts were not equal:
First has 1, Second has 0: 'c\r'
First has 0, Second has 1: 'c'
```
Fix the discrepancy in behavior across the two platforms by
manually stripping Windows newlines before yielding each line in
the test file.
Reviewers: echristo, beanz, ddunbar, delcypher, rnk
Reviewed By: rnk
Subscribers: mehdi_amini, llvm-commits
Differential Revision: https://reviews.llvm.org/D27746
llvm-svn: 309312