RFR: 8258411: Move module set configuration from Modules.gmk to conf dir [v2]

[Alan Bateman]

On Wed, 16 Dec 2020 00:14:02 GMT, Magnus Ihse Bursie <ihse at openjdk.org> wrote:

>> Can any of `INTERIM_IMAGE_MODULES` , `HOTSPOT_MODULES` and `LANGTOOLS_MODULES` be inlined in the appropriate .gmk file?
>> 
>> `INTERIM_IMAGE_MODULES` is for building interim image.  If it has to be defined in a conf file, I like its name be explicit and match the target or makefile, for example, `interim-images.conf` or `InterimImages.conf`.    This way I can tell what this conf file intends for.  What do you think?
>
> @mlchung The entire point of this exercise is to *not* have hard-coded lists of modules in make files... 
> 
> Having hard-coded lists have come back to bite us, time after time again. We try to auto-discover everything that is possible. For these sets of modules, however, auto-discovery is not possible since these lists *define* what we mean by e.g. platform modules or an interim image.

The update to JRE_MODULES in Images.gmk resolves my comment above. However, the naming for the configuration is still a bit odd,  e.g. module-sets-classloaders.conf should be something like module-loader-map.conf as used to generate ModuleLoaderMap.java in the build.

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PR: https://git.openjdk.java.net/jdk/pull/1781