Problem:
RelWithDebInfo generates redundant flags:
Compilation: /usr/bin/cc -O2 -g -Og -g
The `CMAKE_C_FLAGS_RELWITHDEBINFO` variable is being modified in a way
that caused duplicate `-Og` and `-g` flags to be added. The resulting
flags were `-O2 -g -Og -g`.
- `-Og` (Optimize for debugging) and `-O2` (Optimize for performance)
are different optimization levels. We can't use both at once.
- The duplicate `-g` flag is redundant and no effect.
multiple -O flags has no effect for code, just redundant.
> If you use multiple -O options, with or without level numbers, the last such option is the one that is effective.
https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html
Solution:
Adjust the flags to use the more appropriate `-O2 -g`.
Compilation: /usr/bin/cc -O2 -g
BEFORE:
```
:verbose version
NVIM v0.11.0-dev-1443+ge00cd1ab40
Build type: RelWithDebInfo
LuaJIT 2.1.1734355927
Compilation: /usr/bin/cc -O2 -g -Og -g -flto -fno-fat-lto-ob
jects -Wall -Wextra -pedantic -Wno-unused-parameter -Wstrict
...
```
AFTER:
```
:verbose version
NVIM v0.11.0-dev-e00cd1ab4-dirty
Build type: RelWithDebInfo
LuaJIT 2.1.1734355927
Compilation: /usr/bin/cc -O2 -g -flto -fno-fat-lto-objects -
Wall -Wextra -pedantic -Wno-unused-parameter -Wstrict-protot
...
```
`cmake --preset ci`
is equivalent to
`cmake -B build -G Ninja -D CI_BUILD=ON`
Also remove build presets as they're not very useful without workflow
presets, which are only available in schema versions 6 and above.
Workflow presets allows combining configure, build, test and packaging
steps and makes it possible to run everything in a single command. So
cmake --preset iwyu
cmake --build --preset iwyu
instead becomes
cmake --workflow --preset iwyu
Workflow presets requires at least cmake version 3.25 to use.
Allow Include What You Use to remove unnecessary includes and only
include what is necessary. This helps with reducing compilation times
and makes it easier to visualise which dependencies are actually
required.
Work on https://github.com/neovim/neovim/issues/549, but doesn't close
it since this only works fully for .c files and not headers.
This allows a more declarative way of defining targets which may be easier to those not familiar with cmake quirks.
Example usage:
# get a list of pre-configured presets
cmake --list-presets
# configure a preset
cmake . --preset=default
# build it
cmake --build --preset=default
