doc: add alpine build instructions #32559

Why libtool?

I'd add pkgconf.

libressl ?

Crikey that's an old hangover....

I ported initial requirements from my current Alpine Dockerfile

I foolishly assumed this was just the case of Alpine splitting packages more granularly that e.g. Ubuntu, but taking a closer look now suspect this is a hangover from pre 0.12 where we supported SSL on RPC?

Removed in 5332082d009

Thanks, dropped libtool and added pkgconf

Don't think you need m4 here?

Verified correct. thanks

Why?

Can be dropped after #32568.

#32568 landed.

Dropped in 64986e1a44e108628b245ca977d2b8eb69ed5580

FWIW, linux-headers is a dependency of boost-dev on my system.

not even a nit: gmake, which explicitly refers to GNU Make, also works.

However, depends build the systemtap package. The subsequent configuration results in:

# cmake -B build --toolchain depends/x86_64-pc-linux-musl/toolchain.cmake
<snip>
  USDT tracing ........................ ON
<snip>

And the build succeeds.

cc @0xB10C

Did using the tracepoints work? Depends and a build will likely succeed, depends is just copying a header, and the CMake existence check is basic.

I don't have a good way to test this personally, as I'm primarily using alpine in a container. I've therefore updated the comment here to:

User-Space, Statically Defined Tracing (USDT) is not supported or tested on Alpine Linux at this time.

...which I think is more accurate having done more research into systemtap/dtrace/usdt support on Alpine. This doesn't preclude someone from getting it working/documenting the steps in the future.

1. I think we should consider a note from apk:

Executing ninja-build-1.12.1-r1.post-install
* this only installs ninja to /usr/lib/ninja-build/bin/ninja
* add that to your path to use it, or invoke it directly.
* for most uses, you want samurai instead:
*  $ apk add samurai
* which has a "ninja" executable compatible with ninja.

and install samurai. Otherwise, Qt still complains:

CMake Warning at qtbase/cmake/QtBuildHelpers.cmake:12 (message):
  The officially supported CMake generator for building Qt is Ninja / Ninja
  Multi-Config.  You are using: 'Unix Makefiles' instead.  Thus, you might
  encounter issues.  Use at your own risk.

2. Is xz really necessary?

Is xz really necessary?

It's currently pulled in as a cmake dep, but it also seems fine to be explicit.

and install samurai.

Yea, I think we should use samurai here.

Updated to samurai and removed explicit xz (seems preferable to let this be pulled in as a dependency, or not, by cmake) in 4f502baf8f649e30d9495760b54080c272882213

seems preferable to let this be pulled in as a dependency, or not, by cmake

Not sure? It's a dep for Qt, and some of its sub deps. Nothing to do with CMake (just happens to also be pulled in by it).

On Alpine Linux v3.22:

$ apk info -e xz | wc -l
0
$ gmake -C depends freetype_extracted  # Succeeds, just like for any other package with a .tar.xz tarball.