[lit] Respect LLVM_LIT_TOOLS_DIR when looking for 'tar' on Windows.

[ikudrin]

Summary

Changes in D38977 expect 'tar' to be found in one of PATH directories.
On Windows, one might opt to use LLVM_LIT_TOOLS_DIR rather than adding
MSYS tools directory to the PATH. In that case, tests for lld failed on run.

[lichray]

test/lit.cfg.py

90

How about just read with tar_version, _ = communicate() and remove the '.wait()'?

[ikudrin]

test/lit.cfg.py

90

I'd redirect your idea to the author of D38977, @pcc.
Anyway, this patch is only about fixing an execution failure on Windows, and nothing more.

[zturner]

We really should be using llvm_config.get_process_output() here, fwiw, but as you said, this patch is just fixing an execution failure.

[ikudrin]

Thanks! If you don't mind, I'll leave the mentioned improvements to ones who understand python and lit better than me.

test/lit.cfg.py

 # libxml2 to merge manifests.
 if (lit.util.which('cvtres', config.environment['PATH'])) or \
         (config.llvm_libxml2_enabled == '1'):
     config.available_features.add('manifest_tool')
 
 if (config.llvm_libxml2_enabled == '1'):
     config.available_features.add('libxml2')
 
+tar_executable = lit.util.which('tar', config.environment['PATH'])
+if tar_executable:
     tar_version = subprocess.Popen(
-    ['tar', '--version'], stdout=subprocess.PIPE, env={'LANG': 'C'})
+        [tar_executable, '--version'], stdout=subprocess.PIPE, env={'LANG': 'C'})
     if 'GNU tar' in tar_version.stdout.read().decode():
         config.available_features.add('gnutar')
     tar_version.wait()