liblzma enum values added in 5.3.1 and 5.3.2 cause compile warnings

Summary

This is just a small janitorial task I'd like to fix in order to get clean builds (with --enable-fatal-warnings) completing on Debian unstable, which includes liblzma 5.4.1. Both of the alpha releases 5.3.1 and 5.3.2 added new enum values.

Steps to reproduce:

1. ./configure --enable-fatal-warnings
2. make

What is the current bug behavior?

On Debian unstable, with --enable-fatal-warnings, the build fails. (logs below)

What is the expected behavior?

Clean build.

Environment

Git main branch, Debian unstable.

Relevant logs and/or screenshots

src/lib/compress/compress_lzma.c: In function ‘lzma_error_str’:
src/lib/compress/compress_lzma.c:51:3: error: enumeration value ‘LZMA_SEEK_NEEDED’ not handled in switch [-Werror=switch-enum]
   51 |   switch (error) {
      |   ^~~~~~
src/lib/compress/compress_lzma.c:51:3: error: enumeration value ‘LZMA_RET_INTERNAL1’ not handled in switch [-Werror=switch-enum]
src/lib/compress/compress_lzma.c:51:3: error: enumeration value ‘LZMA_RET_INTERNAL2’ not handled in switch [-Werror=switch-enum]
src/lib/compress/compress_lzma.c:51:3: error: enumeration value ‘LZMA_RET_INTERNAL3’ not handled in switch [-Werror=switch-enum]
src/lib/compress/compress_lzma.c:51:3: error: enumeration value ‘LZMA_RET_INTERNAL4’ not handled in switch [-Werror=switch-enum]
src/lib/compress/compress_lzma.c:51:3: error: enumeration value ‘LZMA_RET_INTERNAL5’ not handled in switch [-Werror=switch-enum]
src/lib/compress/compress_lzma.c:51:3: error: enumeration value ‘LZMA_RET_INTERNAL6’ not handled in switch [-Werror=switch-enum]
src/lib/compress/compress_lzma.c:51:3: error: enumeration value ‘LZMA_RET_INTERNAL7’ not handled in switch [-Werror=switch-enum]
src/lib/compress/compress_lzma.c:51:3: error: enumeration value ‘LZMA_RET_INTERNAL8’ not handled in switch [-Werror=switch-enum]
src/lib/compress/compress_lzma.c: In function ‘tor_lzma_compress_process’:
src/lib/compress/compress_lzma.c:282:3: error: enumeration value ‘LZMA_SEEK_NEEDED’ not handled in switch [-Werror=switch-enum]
  282 |   switch (retval) {
      |   ^~~~~~
src/lib/compress/compress_lzma.c:282:3: error: enumeration value ‘LZMA_RET_INTERNAL1’ not handled in switch [-Werror=switch-enum]
src/lib/compress/compress_lzma.c:282:3: error: enumeration value ‘LZMA_RET_INTERNAL2’ not handled in switch [-Werror=switch-enum]
src/lib/compress/compress_lzma.c:282:3: error: enumeration value ‘LZMA_RET_INTERNAL3’ not handled in switch [-Werror=switch-enum]
src/lib/compress/compress_lzma.c:282:3: error: enumeration value ‘LZMA_RET_INTERNAL4’ not handled in switch [-Werror=switch-enum]
src/lib/compress/compress_lzma.c:282:3: error: enumeration value ‘LZMA_RET_INTERNAL5’ not handled in switch [-Werror=switch-enum]
src/lib/compress/compress_lzma.c:282:3: error: enumeration value ‘LZMA_RET_INTERNAL6’ not handled in switch [-Werror=switch-enum]
src/lib/compress/compress_lzma.c:282:3: error: enumeration value ‘LZMA_RET_INTERNAL7’ not handled in switch [-Werror=switch-enum]
src/lib/compress/compress_lzma.c:282:3: error: enumeration value ‘LZMA_RET_INTERNAL8’ not handled in switch [-Werror=switch-enum]

Possible fixes

The new enums seem quite unlikely to matter for Tor, but the existing comments (compress_lzma.c:298) do mention specifically that we are trying to keep the switch-enum warning in place so that we have an exhaustive list of the return codes that were defined at compile-time.

It may be worth reconsidering this approach and going with -Wno-error=switch-enum here, but we can safely add the new enums under LZMA_VERSION guards at the cost of just a little more verbosity in this code. That's the approach I would implement unless others have objections to the clutter.