Update version of proc-macro2

[leftwo]

proc-macro2 needed an update:

alan@atrium:helios$ cd tools/helios-build/
alan@atrium:helios-build$ cargo build
   Compiling proc-macro2 v1.0.53                                                 
   Compiling h2 v0.3.16
error[E0635]: unknown feature `proc_macro_span_shrink`
  --> /home/alan/.cargo/registry/src/index.crates.io-6f17d22bba15001f/proc-macro2
-1.0.53/src/lib.rs:92:30                                                         
   |                                                                             
92 |     feature(proc_macro_span, proc_macro_span_shrink)
   |                              ^^^^^^^^^^^^^^^^^^^^^^
                                                                                 
For more information about this error, try `rustc --explain E0635`.

After cargo update proc-macro2, I could build again.

[leftwo]

Oh, looks like there are other places that need it too:

Sep 27 17:56:38.960 INFO E| Compiling ucd-trie v0.1.5                            
Sep 27 17:56:38.997 INFO E| error[E0635]: unknown feature `proc_macro_span_shrink`                                                                                
Sep 27 17:56:38.997 INFO E| --> /home/alan/.cargo/registry/src/index.crates.io-6f17d22bba15001f/proc-macro2-1.0.56/src/lib.rs:92:30                               
Sep 27 17:56:38.997 INFO E| |                                                    
Sep 27 17:56:38.997 INFO E| 92 |     feature(proc_macro_span, proc_macro_span_shrink)                                                                             
Sep 27 17:56:38.997 INFO E| |                              ^^^^^^^^^^^^^^^^^^^^^^
Sep 27 17:56:39.124 INFO E| Compiling crossbeam-epoch v0.9.13
Sep 27 17:56:39.136 INFO E| Compiling num_threads v0.1.6                         
Sep 27 17:56:39.137 INFO E| Compiling time-macros v0.2.8                         
Sep 27 17:56:39.156 INFO E| For more information about this error, try `rustc --explain E0635`.                                                                   
Sep 27 17:56:39.195 INFO E| error: could not compile `proc-macro2` (lib) due to previous error                                                                    
Sep 27 17:56:39.195 INFO E| warning: build failed, waiting for other jobs to finish...                                                                            
Error: exec ["cargo", "build", "--locked", "--release"]: failed ExitStatus(unix_wait_status(25856))                                                               
gmake: *** [Makefile:42: setup] Error 1 

Let me go find those as well.

[leftwo]

It was pilot that needed the update, but after I updated

  569  cd projects/pilot/
  570  ls
  571  cargo build
  572  cargo update proc-macro2
  573  cargo build

Nothing showed up in git status that indicated a changed file under revision control.
🤷