[frontend] Pretty-print ptxas command on failure (#4882)

Super quick quality-of-life improvement: on `ptxas` failure we were just
dumping the repro command as a list, and joining it before printing
makes it much easier to copy-and-paste for debugging.

Author: bertmaher

third_party/nvidia/backend/compiler.py

@@ -359,7 +359,7 @@ def make_cubin(src, metadata, opt, capability):
 
                 raise RuntimeError(f'{error}\n'
                                    f'`ptxas` stderr:\n{log}\n'
-                                   f'Repro command: {ptxas_cmd}\n')
+                                   f'Repro command: {" ".join(ptxas_cmd)}\n')
 
             with open(fbin, 'rb') as f:
                 cubin = f.read()