[test] Use system locale for mri-utf8.test

Summary:
llvm-ar's mri-utf8.test test relies on the en_US.UTF-8 locale to be
installed for its last RUN line to work. If not installed, the unicode
string gets encoded (interpreted) as ascii which fails since the most
significant byte is non zero. This commit changes the test to only rely
on the system being able to encode the pound sign in its default
encoding (e.g. UTF-16 for Microsoft Windows) by always opening the file
via input/output redirection. This avoids forcing a given locale to be
present and supported. A Byte Order Mark is also added to help
recognizing the encoding of the file and its endianness.

Reviewers: gbreynoo, MaskRay, rupprecht, JamesNagurne, jfb

Subscribers: dexonsmith, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D68472

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@374318 91177308-0d34-0410-b5e6-96231b3b80d8

Author: Thomas Preud'homme

test/tools/llvm-ar/mri-nonascii.test

@@ -0,0 +1,22 @@
+# Test non-ascii archive members
+# XFAIL: system-darwin
+
+RUN: rm -rf %t && mkdir -p %t/extracted
+
+# Note: lit's Python will read this UTF-8 encoded mri-nonascii.txt file,
+# decode it to unicode. The filename in the redirection below will then
+# be encoded in the system's filename encoding (e.g. UTF-16 for
+# Microsoft Windows).
+RUN: echo "contents" > %t/£.txt
+
+RUN: echo "CREATE %t/mri.ar" > %t/script.mri
+RUN: echo "ADDMOD %t/£.txt" >> %t/script.mri
+RUN: echo "SAVE" >> %t/script.mri
+
+RUN: llvm-ar -M < %t/script.mri
+RUN: cd %t/extracted && llvm-ar x %t/mri.ar
+
+# Same as above.
+RUN: FileCheck --strict-whitespace %s <£.txt
+CHECK:{{^}}
+CHECK-SAME:{{^}}contents{{$}}