MDEV-40608 MariaDB-devel is incomplete for plugins

[vuvova]

create and install mariadb-plugin-config.cmake

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[vuvova]

@vaintroub FYI, it's a draft, I'm not proposing it for a merge yet. But see the direction.
With that a plugin needs find_project(mariadb-plugin REQUIRED) and MARIADB_ADD_PLUGIN() to be buildable with cmake . && make, no server sources required.

[Copilot]

Pull request overview

Adds an installable CMake config intended to make the MariaDB development package usable for building plugins, and refactors plugin CMake plumbing to support that packaging.

Changes:

• Introduces support-files/mariadb-plugin-config.cmake.in and installs the configured result into ${INSTALL_SHAREDIR}/cmake/mariadb-plugin/.
• Refactors plugin discovery to live in the top-level CMakeLists.txt and introduces VERIFY_PLUGINS() in cmake/plugin.cmake.
• Renames the primary plugin macro to MARIADB_ADD_PLUGIN while keeping MYSQL_ADD_PLUGIN as a compatibility wrapper.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
support-files/mariadb-plugin-config.cmake.in	New installed CMake config template intended for plugin consumers.
support-files/CMakeLists.txt	Generates/installs the new plugin config CMake file.
CMakeLists.txt	Moves plugin subdirectory enumeration into the top-level build and calls VERIFY_PLUGINS().
cmake/plugin.cmake	Introduces MARIADB_ADD_PLUGIN, keeps MYSQL_ADD_PLUGIN wrapper, and adds VERIFY_PLUGINS().
.gitignore	Ignores the generated support-files/mariadb-plugin-config.cmake.

[vuvova]

not so easy. I need to try it on a plugin with tests

[vaintroub]

@vaintroub FYI, it's a draft, I'm not proposing it for a merge yet. But see the direction. With that a plugin needs find_project(mariadb-plugin REQUIRED) and MARIADB_ADD_PLUGIN() to be buildable with cmake . && make, no server sources required.

you mean "find_package(mariadb-plugin CONFIG REQUIRED)" . Yes, I thought about something like that