Add flex to docker for building bpf module on recent amazon linux2

[schans]

Flex is needed for building bpf module on recent amazon linux images.

#1558

What type of PR is this?

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/kind bug

/kind cleanup

/kind design

/kind documentation

/kind failing-test

/kind feature

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/kind rule-update

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Any specific area of the project related to this PR?

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/area build

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What this PR does / why we need it:
The bpf module fails to build on recent amazon linux2 versions with docker (k8s) deploys.

Which issue(s) this PR fixes:
#1558

Fixes #1558

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

fix(docker/falco): add flex and bison dependency to container image

[schans]

/assign @leogr

[leogr]

👍

[poiana]

LGTM label has been added.

Git tree hash: 151d00e663a34aa782fab9bc78eb6471827bedaf

[leogr]

/milestone 0.28.0

[leogr]

/cc @leodido

[leodido]

LGTM

We should also add bison. Left a suggestion

[leogr]

Hey @schans,

Could you sign-off the last commit pls?

[schans]

Hi @leodido ,

I have added bison, squashed the commits and added the sign off. Hopefully we're good to go ;-)

[leogr]

Thank you!

[poiana]

LGTM label has been added.

Git tree hash: 9f97b2d2201ad6c0ea8e970c58b36ad95ef29f17

[schans]

Looks like we are really close to merging ;-) Anything I can do to help to push this over the line?

[leogr]

Looks like we are really close to merging ;-) Anything I can do to help to push this over the line?

You did already a lot! :)

Now we have just to wait for another maintainer who will double-check and approve eventually. I'm confident that will happen within the 0.28.0 time window. 👍

Thank you again

[poiana]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: leodido, leogr

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