[PATCH v3] meson: regenerate config-list.h when Documentation changes

The Meson-based build doesn't know when to rebuild config-list.h, so the header is sometimes stale.

For example, an old build directory might have config-list.h from before 4173df5187 (submodule: introduce extensions.submodulePathConfig, 2026-01-12), which added submodule.<name>.gitdir to the list. Without it, t9902-completion.sh fails. Regenerating the config-list.h artifact from sources fixes the artifact and the test.

Teach the meson build to depend on the Documentation files that generate-configlist.sh reads by having it an additional output as a list of dependency files, since Meson does not have (or want) builtin support for globbing like Make.

Helped-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: D. Ben Knoble <ben.knoble+github@gmail.com>
---

Notes (benknoble/commits):
    Changes from v2 (<c9ae171eed6bd5b0fa6671b10a5ad0da024f36d0.1770649805.git.ben.knoble+github@gmail.com>):
    
    • Pick up (and tweak) Patrick's depfile proposal
    • Include the script itself as a dependency
    • Escape output paths (spaces, octothorpes, and backslashes) for Ninja
    
    I'm not 100% sure I've actually done the escaping correctly, though,
    since Ninja's source says that a space preceded by 2N backslashes
    represents 2N backslashes at the end of a filename, and
    
        λ printf '%s\n' 'foo\' | sed 's/[# \\]/\\&/g' | xxd
        00000000: 666f 6f5c 5c0a                           foo\\.
    
    So would they interpret that as the filename 'foo\\' instead of 'foo\' ?
    (Or, no because the 2N slashes aren't followed by a SP, but a NL?)

 generate-configlist.sh | 10 +++++++++-
 meson.build            |  4 +++-
 2 files changed, 12 insertions(+), 2 deletions(-)