[dexter] Fix feature tests on Windows

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.

Reviewers: jmorse

Differential Revision: https://reviews.llvm.org/D69725

debuginfo-tests/CMakeLists.txt

@@ -13,6 +13,11 @@ set(DEBUGINFO_TEST_DEPS
   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)

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

@@ -80,12 +80,14 @@ def run_external_build_script(context, script_path, source_files,
                 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))
 

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

@@ -1,4 +1,4 @@
-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!