scope to only DYLD env vars

Author: keith

llvm/utils/lit/lit/TestRunner.py

@@ -1227,9 +1227,13 @@ def executeScript(test, litConfig, tmpBase, commands, cwd):
         if test.config.pipefail:
             f.write(b"set -o pipefail;" if mode == "wb" else "set -o pipefail;")
 
+        # Manually export any DYLD_* variables used by dyld on macOS because
+        # otherwise they are lost when the shell executable is run, before the
+        # lit test is executed.
         env_str = "\n".join(
             "export {}={};".format(k, shlex.quote(v))
             for k, v in test.config.environment.items()
+            if k.startswith("DYLD_")
         )
         f.write(bytes(env_str, "utf-8") if mode == "wb" else env_str)
         f.write(b"set -x;" if mode == "wb" else "set -x;")