[dexter] Fix feature tests on Windows

[rnk]

Summary

First, add LLD as a dependency on Windows. The windows batch scripts
pass -fuse-ld=lld, so they need it.

Second, decode builder stdout/stderr even if the command fails.
Otherwise it gets printed as b'line 1\n\rline 2\n\r'.

Last, make the batch script one line less noisy. We might want to try to
do more here, though. It would be nice if we could get as close to
possible as lit, where you can literally copy & paste the failing
command to re-run it.

With the two changes above, now the feature tests that use clang++.bat
pass for me. The clang-cl_vs2015 ones still fail, and I'll fix them
separately.

[jmorse]

LGTM

debuginfo-tests/CMakeLists.txt

 # Debug Info tests.  These tests invoke clang to generate programs with
 # various types of debug info, and then run those programs under a debugger
 # such as GDB or LLDB to verify the results.
 
 set(DEBUGINFO_TESTS_SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR})
 set(DEBUGINFO_TESTS_BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR})
 
 set(DEBUGINFO_TEST_DEPS
   clang
   FileCheck
   count
   llvm-objdump
   not
   )
 
+# The Windows builder scripts pass -fuse-ld=lld.
+if (WIN32)
+  set(DEBUGINFO_TEST_DEPS ${DEBUGINFO_TEST_DEPS} lld)
+endif()
+
 # If we don't already have Python 3, throw away any previous results and try to
 # find it again.
 set(DEBUGINFO_UNSET_PYTHON3 OFF)
 if (PYTHON_VERSION_MAJOR LESS 3)
   unset(PYTHONINTERP_FOUND CACHE)
   unset(PYTHON_EXECUTABLE CACHE)
   unset(PYTHON_LIBRARY CACHE)
   unset(PYTHON_DLL CACHE)

debuginfo-tests/dexter/dex/builder/Builder.py

try:
             process = subprocess.Popen(
                 [script_path],
                 cwd=context.working_directory.path,
                 env=env,
                 stdout=subprocess.PIPE,
                 stderr=subprocess.PIPE)
             out, err = process.communicate()
             returncode = process.returncode
+        out = out.decode('utf-8')
+        err = err.decode('utf-8')
         if returncode != 0:
             raise BuildScriptException(
                 '{}: failed with returncode {}.\nstdout:\n{}\n\nstderr:\n{}\n'.
                 format(script_path, returncode, out, err),
                 script_error=err)
-        return out.decode('utf-8'), err.decode('utf-8'), builderIR
+        return out, err, builderIR
     except OSError as e:
         raise BuildScriptException('{}: {}'.format(e.strerror, script_path))
 
 
 class TestBuilder(unittest.TestCase):
     def test_get_script_environment(self):
         source_files = ['a.a', 'b.b']
         compiler_options = ['-option1 value1', '-option2 value2']

debuginfo-tests/dexter/dex/builder/scripts/windows/clang.bat

-setlocal EnableDelayedExpansion
+@setlocal EnableDelayedExpansion
 
 for %%I in (%SOURCE_INDEXES%) do (
   %PATHTOCLANGPP% -fuse-ld=lld -c !COMPILER_OPTIONS_%%I! !SOURCE_FILE_%%I! -o !OBJECT_FILE_%%I!
   if errorlevel 1 goto :FAIL
 )
 
 %PATHTOCLANGPP% -fuse-ld=lld %LINKER_OPTIONS% %OBJECT_FILES% -o %EXECUTABLE_FILE%
 if errorlevel 1 goto :FAIL
 goto :END
 
 :FAIL
 echo FAILED
 exit /B 1
 
 :END
 exit /B 0