Re: [PATCH] ci: perform build and smoke tests for Meson docs

> The documentation CI job should only build the documentation, but
> these meson commands unnecessarily compile git as well:
> 
> https://github.com/git/git/actions/runs/17222438141/job/48860520663#step:4:4679
> 
>   + meson compile -C build-asciidoc
>   ninja: Entering directory `/home/runner/work/git/git/build-asciidoc'
>   [1/1327] Generating hook-list.h with a custom command
>   [2/1327] Generating config-list.h with a custom command
>   [3/1327] Generating GIT-VERSION-FILE with a custom command (wrapped by meson to set env)
>   [4/1327] Generating command-list.h with a custom command
>   [5/1327] Generating version-def.h with a custom command (wrapped by meson to set env)
>   [6/1327] Generating Documentation/asciidoc.conf with a custom command (wrapped by meson to set env)
>   [7/1327] Generating t/clar-decls.h with a custom command
>   [8/1327] Generating Documentation/cmds-ancillaryinterrogators.adoc with a custom command
>   [9/1327] Generating Documentation/mergetools-diff.adoc with a custom command (wrapped by meson to set env)
>   [10/1327] Compiling C object libcommon-main.a.p/common-main.c.o
>   [11/1327] Compiling C object libgit.a.p/alias.c.o
>   [12/1327] Compiling C object libgit.a.p/advice.c.o
>   [13/1327] Compiling C object libgit.a.p/abspath.c.o