Keep gyb from messing up line endings on Windows

GYB opens its inputs and outputs in text mode. This is a problem because the recommendation in Windows is to check everything out in LF mode to avoid breaking tests, so gybbing a file ends up converting LFs to CRLFs. That broke test/SILGen/magic_identifier_file_conflicting.swift.gyb.

Modify GYB to open its files in binary mode instead of text mode. This is a no-op everywhere but Windows.

Note that this change is incomplete: it’s somewhat difficult to switch stdin and stdout to binary mode in Python 2. I’ve added FIXME comments about this.

Author: beccadax

test/SILGen/magic_identifier_file_conflicting.swift.gyb

@@ -1,5 +1,5 @@
 // RUN: %empty-directory(%t)
-// RUN: %gyb -D TEMPDIR=%t %s > %t/magic_identifier_file_conflicting.swift
+// RUN: %gyb -D TEMPDIR=%t %s -o %t/magic_identifier_file_conflicting.swift
 
 // We want to check both the diagnostics and the SIL output.
 // RUN: %target-swift-emit-silgen -verify -emit-sorted-sil -enable-experimental-concise-pound-file -module-name Foo %t/magic_identifier_file_conflicting.swift %S/Inputs/magic_identifier_file_conflicting_other.swift | %FileCheck %s

utils/gyb.py

@@ -1208,12 +1208,13 @@ def succ(a):
         help='''Bindings to be set in the template's execution context''')
 
     parser.add_argument(
-        'file', type=argparse.FileType(),
+        'file', type=argparse.FileType('rb'),
         help='Path to GYB template file (defaults to stdin)', nargs='?',
-        default=sys.stdin)
+        default=sys.stdin)    # FIXME: stdin not binary mode on Windows
     parser.add_argument(
-        '-o', dest='target', type=argparse.FileType('w'),
-        help='Output file (defaults to stdout)', default=sys.stdout)
+        '-o', dest='target', type=argparse.FileType('wb'),
+        help='Output file (defaults to stdout)',
+        default=sys.stdout)    # FIXME: stdout not binary mode on Windows
     parser.add_argument(
         '--test', action='store_true',
         default=False, help='Run a self-test')