scripts/gen_compile_commands: update to Linux v6.7

Adds support for assembly files and updates the LINE_PATTERN so it
supports both "cmd" and "savedcmd", which allows reverting the U-Boot
modification in commit 97fbb2eb016b ("scripts/gen_compile_commands.py:
adapt _LINE_PATTERN").

Upstream commits:

- 880946158b011 gen_compile_commands.py: fix path resolve with symlinks in it
- 9e56d3be4bfd2 gen_compile_commands: Sort output compile commands by file name
- 52c15e7e79285 gen_compile_commands: Allow the line prefix to still be cmd_
- 1c67921444bf6 gen_compile_commands: add assembly files to compilation database

Signed-off-by: Brandon Maier <brandon.maier@collins.com>
Cc: Joao Marcos Costa <jmcosta944@gmail.com>

scripts/gen_compile_commands: fix usage message

Replace mentions to 'kernel' by 'U-Boot' to avoid confusion.

Signed-off-by: Joao Marcos Costa <jmcosta944@gmail.com>
Tested-by: Joao Paulo Goncalves <joao.goncalves@toradex.com>

doc: add documentation for gen_compile_commands.py

This documentation briefly explains what is a compilation database,
and how to use the script to generate one.

This is not a portage, as there was no original documentation in the
Linux sources.

Acknowledge the documentation in the script's header and in doc/build
index.

Signed-off-by: Joao Marcos Costa <jmcosta944@gmail.com>
Tested-by: Joao Paulo Goncalves <joao.goncalves@toradex.com>

scripts/gen_compile_commands.py: add acknowledgments

Add acknowledgments for porting and modifying the script. Of course, the
license, author, and copyright notice remain the same as in the original
script.

Signed-off-by: Joao Marcos Costa <jmcosta944@gmail.com>
Tested-by: Joao Paulo Goncalves <joao.goncalves@toradex.com>

scripts/gen_compile_commands.py: fix docstring

The referred tool is now in U-Boot. Replace "the Linux kernel" by
"U-Boot" to make the docstring coherent.

Signed-off-by: Joao Marcos Costa <jmcosta944@gmail.com>
Tested-by: Joao Paulo Goncalves <joao.goncalves@toradex.com>

scripts/gen_compile_commands.py: adapt _LINE_PATTERN

For U-Boot's context, the regular expression defined by _LINE_PATTERN
should be adapted. Replace 'savedcmd' by 'cmd'.

Signed-off-by: Joao Marcos Costa <jmcosta944@gmail.com>
Tested-by: Joao Paulo Goncalves <joao.goncalves@toradex.com>

scripts: Port Linux's gen_compile_commands.py to U-Boot

This script generates a database of compiler flags, namely
compile_commands.json. It is quite useful for text editors that use
clangd LSP (e.g. Vim, Neovim).

It was ported from Linux's sources:
- tag: v6.4
- revision 6995e2de6891c724bfeb2db33d7b87775f913ad1

Modifications for U-Boot compatibility will be added in a follow-up
commit.

Signed-off-by: Joao Marcos Costa <jmcosta944@gmail.com>
Tested-by: Joao Paulo Goncalves <joao.goncalves@toradex.com>

scripts/gen_compile_commands: fix usage message

Replace mentions to 'kernel' by 'U-Boot' to avoid confusion.

Signed-off-by: Joao Marcos Costa <jmcosta944@gmail.com>
Tested-by: Joao Paulo Goncalves <joao.goncalves@toradex.com>

doc: add documentation for gen_compile_commands.py

This documentation briefly explains what is a compilation database,
and how to use the script to generate one.

This is not a portage, as there was no original documentation in the
Linux sources.

Acknowledge the documentation in the script's header and in doc/build
index.

Signed-off-by: Joao Marcos Costa <jmcosta944@gmail.com>
Tested-by: Joao Paulo Goncalves <joao.goncalves@toradex.com>

scripts/gen_compile_commands.py: add acknowledgments

Add acknowledgments for porting and modifying the script. Of course, the
license, author, and copyright notice remain the same as in the original
script.

Signed-off-by: Joao Marcos Costa <jmcosta944@gmail.com>
Tested-by: Joao Paulo Goncalves <joao.goncalves@toradex.com>

scripts/gen_compile_commands.py: fix docstring

The referred tool is now in U-Boot. Replace "the Linux kernel" by
"U-Boot" to make the docstring coherent.

Signed-off-by: Joao Marcos Costa <jmcosta944@gmail.com>
Tested-by: Joao Paulo Goncalves <joao.goncalves@toradex.com>

scripts/gen_compile_commands.py: adapt _LINE_PATTERN

For U-Boot's context, the regular expression defined by _LINE_PATTERN
should be adapted. Replace 'savedcmd' by 'cmd'.

Signed-off-by: Joao Marcos Costa <jmcosta944@gmail.com>
Tested-by: Joao Paulo Goncalves <joao.goncalves@toradex.com>

scripts: Port Linux's gen_compile_commands.py to U-Boot

This script generates a database of compiler flags, namely
compile_commands.json. It is quite useful for text editors that use
clangd LSP (e.g. Vim, Neovim).

It was ported from Linux's sources:
- tag: v6.4
- revision 6995e2de6891c724bfeb2db33d7b87775f913ad1

Modifications for U-Boot compatibility will be added in a follow-up
commit.

Signed-off-by: Joao Marcos Costa <jmcosta944@gmail.com>
Tested-by: Joao Paulo Goncalves <joao.goncalves@toradex.com>