R2021b+ / log4j 2.x compatibility

[apjanke]

Get SLF4M working with Matlab R2021b and newer releases that are shipping log4j 2.x instead of 1.x.

Blocks #7. This ticket is essentially the same issue, but is where I'm going to be tracking my work and leaving a bunch of detailed comments, and I don't want to spam our users with a bunch of comment notifications.

My current approach is to build customized, package-name-munged forks of the SLF4J and Log4j 1.2.x libraries, vendor them with SLF4M, and conditionally pull them in at run time based on the version of Matlab being used. These munged libraries are a large enough project that I'm creating them in a new separate "slf4m-jankalog" repo. The resulting JARs will be copied in to the main SLF4M repo. That'll keep things tidy.

Subtasks

• Munged opp SLF4J and log4j library building slf4m-jankalog#4
  • (Main issue for this whole project, in the other "jankalog" repo.)
• R2021a+: Dynamic selection of slf4j/log4j libs #16
• Upgrade to newer log4j 1.2.x for munged library? #17
• log4j 1.2.15: have ant clean also clean the tests/ subdir slf4m-jankalog#3

References

• SLF4M busted under R2022a or R2021b - log4j upgrade #7
• MathWorks Tech Support cases 05490191, 05479210
• Matlab jarext JAR version list