Fix running from non-standard mounts like /eos/user

Part of fixing LbEnv#48 (closed)

LbPlatformUtils/debug.py

@@ -184,12 +184,20 @@ def check_apptainer(results):
 
 def run_cmd(results, command):
     cmd = join_cmd(command)
+
+    # Having PWD set causes some versions of apptainer to ignore the current
+    # working directory and, if the path in PWD contains symlinks, apptainer can
+    # fail to set the current working directory correctly and default to $HOME.
+    env = os.environ.copy()
+    env.pop("PWD", None)
+
     try:
         proc = subprocess.Popen(
             command,
             stdout=subprocess.PIPE,
             stderr=subprocess.PIPE,
             universal_newlines=True,
+            env=env,
         )
         stdout, stderr = proc.communicate()
     except FileNotFoundError: