build: Fix release builds with enabled FLB_DEBUG

[Garfield96]

Enabling FLB_RELEASE should enable compiler optimizations. However, if FLB_DEBUG (enabled by default) was enabled at the same time, no optimization settings were applied. Now, FLB_RELEASE will always enable optimizations and includes debug information (CMAKE_BUILD_TYPE is RelWithDebInfo).

This issue affects all published Docker images and most likely severely degrades performance.

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Testing
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• [N/A] Example configuration file for the change
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• [N/A] Attached Valgrind output that shows no leaks or memory corruption was found

If this is a change to packaging of containers or native binaries then please confirm it works for all targets.

• [N/A] Run local packaging test showing all targets (including any new ones) build.
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Documentation

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Backporting

• Backport to latest stable release.

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Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.

[patrick-stephens]

Probably want to target 2.1 branch as well @Garfield96 as this will go into 2.2 otherwise.

[Garfield96]

Hi @patrick-stephens,
thanks for the fast review. I'll create a backport PR for the 2.1 branch (https://github.com/fluent/fluent-bit/tree/2.1).

[Garfield96]

Hi @patrick-stephens,
the test failure looks unrelated. It would be great if this bug fix would be included in the next release. Could you please merge this PR and the backport PR (#8068). Thanks

[Garfield96]

@niedbalski @patrick-stephens
Sorry for asking again, but is there anything preventing this and the backport PR from getting merged?

[patrick-stephens]

Just the size of the review queue is probably the only blocker @Garfield96 , I'll ping @niedbalski on it

[Garfield96]

@patrick-stephens @niedbalski I understand that there is a huge number of open PRs and it takes a considerable amount of time to review them. However, the long review times are slowly becoming a problem, because users are forced to build fluent-bit locally in order to have their features included, and people refrain from contributing. This PR, which changes 2 LOCs, is open for 3 months and my other PR #6087 is open for almost 1.5 years.
Can you provide some plan on how we want to proceed with these PRs?

[edsiper]

my apologies for the delay on this, thanks @patrick-stephens for the heads up.

thanks for the fix, indeed the code is wrongly evaluating FLB_DEBUG first before FLB_RELEASE