Use build tags to make it compile on non linux platforms

[sylr]

What this PR does / why we need it:

Useful when developing on a non linux platform and you want to make sure locally that your changes build.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Which issue/s this PR fixes

How Has This Been Tested?

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I've read the CONTRIBUTION guide
• I have added tests to cover my changes.
• All new and existing tests passed.

[k8s-ci-robot]

Hi @sylr. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[aledbf]

Useful when developing on a non linux platform and you want to make sure locally that your changes build.

Not sure this change makes sense. If we merge this change someone could think the ingress controller runs in a different platform than linux.

Why you don't just use make build?

[sylr]

@aledbf It also fixes a warning thrown by VSCODE because libcontainercgroups.FindCgroupMountpoint() is not found on MacOS.

[aledbf]

/ok-to-test

[aledbf]

/retest

[codecov-commenter]

Codecov Report

Merging #5703 into master will increase coverage by 0.17%.
The diff coverage is 57.89%.

@@            Coverage Diff             @@
##           master    #5703      +/-   ##
==========================================
+ Coverage   58.48%   58.65%   +0.17%     
==========================================
  Files          88       88              
  Lines        6975     6951      -24     
==========================================
- Hits         4079     4077       -2     
+ Misses       2446     2425      -21     
+ Partials      450      449       -1     

Impacted Files	Coverage Δ
internal/ingress/controller/nginx.go	30.00% <0.00%> (+0.27%)	⬆️
internal/ingress/controller/process/nginx.go	100.00% <ø> (+67.64%)	⬆️
internal/ingress/controller/template/template.go	79.73% <61.11%> (+0.05%)	⬆️
cmd/nginx/main.go	5.37% <0.00%> (-0.25%)	⬇️

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[aledbf]

/retest

[aledbf]

/test pull-ingress-nginx-e2e-1-15

[aledbf]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: aledbf, sylr

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• OWNERS [aledbf]

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