Check that `sbeppc_compile_schema` correctly sets target dependencies

[OleksandrKvl]

Experiencing a strange issue locally, changing sbeppc source code doesn't lead to automatic schema recompilation and following test rebuild. When schema XML is changed, it's recompiled but test is not rebuilt, it gets so only on the next build command. Not sure it behaved like this with previous CMake versions (now I have 3.29.1).

Expected behavior is that changing either sbeppc or schema XML should lead to schema recompilation and test rebuild.

[OleksandrKvl]

As explained here, current approach is not bullet-proof, it doesn't work well with Ninja. There are couple of options:

• add sbeppc CLI parameter to inject #include <anchor_file> into each generated file to establish deps
• read and parse XML schema using CMake file(READ) to get schema name from it
• add sbeppc CLI parameter to get schema name and use execute_process to run it

The last 2 options require adding schema file to CMAKE_CONFIGURE_DEPENDS to force re-configuration if it changes.

[OleksandrKvl]

execute_process approach is not an option because it's not possible to pass $<TARGET_NAME:sbepp::sbeppc> to it. Writing XML parser using CMake is simply not feasible, another option is to use regular expressions but it's not bullet-proof. Injecting anchor file include is the most robust and simple approach here.