Extend OMR PR Testing Cmdline

[babsingh]

Recently, there have been PRs where the code is disabled by default via preprocessor flags:

• https://github.com/eclipse/omr/pull/6433
• https://github.com/eclipse/omr/pull/6390

The PR builds do not have an option to enable preprocessor flags, which prevents such changes to be tested. Example: jenkins build cflags="-DDUMP_DBG" cxxflags="-DDUMP_DBG" all.

Based upon the discussion in this week's OMR architecture meeting (https://github.com/eclipse/omr/issues/6416), there are TWO OPTIONS:

1. Aliases. e.g. jenkins build all mode=debug.
2. Pass pre-processor flags via cmd line option. e.g. jenkins build all cflags+="-DDUMP_DBG" cxxflags-="-DDUMP_DBG".

[Option 1] Aliases pros:

• Easy to use for configurations where many preprocessor flags need to be manipulated.

[Option 1] Aliases cons:

• More effort in implementing and maintaining aliases.
• New flags will have to be introduced through an alias before they can be invoked in a PR build.

[Option 2] Cmdline option pros:

• Can immediately accommodate new flags.
• Easier and quicker to implement.
• Less maintenance since there will be no alias configs to maintain.

[Option 2] Cmdline option cons:

• Difficult to use for complicated configurations.

Security (e.g. execution of malicious code via injection) is not a major concern because PR builds can only be launched by a select trusted individuals.

[babsingh]

fyi @0xdaryl @dsouzai @mstoodle @AdamBrousseau

Issue opened for further discussion.

[dsouzai]

(Continuing discussion from the meeting) I suppose it probably does make sense to just have the build flags explicitly passed in for now, and then after some period of time (say a year or something like that) we can create aliases based on the most commonly used flags for convenience (if applicable). At the moment we'd just be guessing as to what the aliases should be. I do think the aliases are a good idea from a human factors pov, but it should also be data driven.

For the sake of having a standard bar of acceptance though, I do think what @mstoodle said should be enforced, namely, even if builds launched with custom flag(s) pass, the PR should only be merged if builds without the custom flag(s) also pass.