gcc10 LTO - Only specify adhlns assembler options at link time

[zvecr]

Description

Resolves the long standing issue of,

Making lets_split/sockets with keymap default                                                          [WARNINGS]
 | 
 | lto-wrapper: warning: Options to Xassembler do not match: -adhlns=.build/obj_lets_split_sockets_default/keyboards/lets_split/lets_split.lst, -adhlns=.build/obj_lets_split_sockets_default/keyboards/lets_split/sockets/sockets.lst, dropping all -Xassembler and -Wa options.
 |

447ec8f - Do the vast majority of users actually care about these files? Seems like it should be opt-in (which also removes an additional clang check).

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout/userspace (addition or update)
• Documentation

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).

[KarlK90]

I think this should be an opt-in by default. 👍