[OpenMP] Fix python3 compatibility in openmp's lit.cfg

Differential Revision: https://reviews.llvm.org/D95669

GitOrigin-RevId: c3c02d0d5a313272f6d35926bdf678fc6b884c02
diff --git a/runtime/test/lit.cfg b/runtime/test/lit.cfg
index 0d4a610..c4e5fe1 100644
--- a/runtime/test/lit.cfg
+++ b/runtime/test/lit.cfg
@@ -76,7 +76,7 @@
   cmd = subprocess.Popen(['xcrun', '--show-sdk-path'],
                          stdout=subprocess.PIPE, stderr=subprocess.PIPE)
   out, err = cmd.communicate()
-  out = out.strip()
+  out = out.strip().decode()
   res = cmd.wait()
   if res == 0 and out:
     config.test_flags += " -isysroot " + out