chore: cleanup CMake dependencies

[federico-sysdig]

What type of PR is this?
/kind cleanup

Any specific area of the project related to this PR?
/area build

Does this PR require a change in the driver versions?
no

What this PR does / why we need it:
It removes some unneeded CMake inclusions and fixes the value of variable ZLIB_SRC which I found to be empty in some build scenarios when reaching the build of the bundled library libelf.

Which issue(s) this PR fixes:
None

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

NONE

[github-actions]

Perf diff from master - unit tests

     5.47%     -1.12%  [.] next
     1.25%     -1.00%  [.] sinsp_evt::get_param
     2.96%     +0.90%  [.] gzfile_read
     6.18%     +0.84%  [.] sinsp::next
    10.50%     -0.76%  [.] sinsp_parser::reset
     4.27%     +0.71%  [.] sinsp_evt::get_type
     2.80%     +0.67%  [.] sinsp_thread_manager::get_thread_ref
     2.23%     -0.66%  [.] scap_event_decode_params
     1.67%     -0.64%  [.] std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::_M_construct<char*>
     1.15%     +0.54%  [.] sinsp_parser::parse_context_switch

Heap diff from master - unit tests

peak heap memory consumption: 0B
peak RSS (including heaptrack overhead): 0B
total memory leaked: 0B

Heap diff from master - scap file

peak heap memory consumption: 0B
peak RSS (including heaptrack overhead): 0B
total memory leaked: 0B

Benchmarks diff from master

Comparing gbench_data.json to /root/actions-runner/_work/libs/libs/build/gbench_data.json
Benchmark                                                         Time             CPU      Time Old      Time New       CPU Old       CPU New
----------------------------------------------------------------------------------------------------------------------------------------------
BM_sinsp_split_mean                                            -0.0085         -0.0085           148           147           148           146
BM_sinsp_split_median                                          -0.0178         -0.0178           149           146           149           146
BM_sinsp_split_stddev                                          -0.7084         -0.7082             3             1             3             1
BM_sinsp_split_cv                                              -0.7059         -0.7057             0             0             0             0
BM_sinsp_concatenate_paths_relative_path_mean                  +0.0532         +0.0532            57            60            57            60
BM_sinsp_concatenate_paths_relative_path_median                +0.0431         +0.0431            58            60            58            60
BM_sinsp_concatenate_paths_relative_path_stddev                -0.5507         -0.5508             1             0             1             0
BM_sinsp_concatenate_paths_relative_path_cv                    -0.5734         -0.5735             0             0             0             0
BM_sinsp_concatenate_paths_empty_path_mean                     +0.0144         +0.0144            23            24            23            24
BM_sinsp_concatenate_paths_empty_path_median                   +0.0087         +0.0087            23            24            23            24
BM_sinsp_concatenate_paths_empty_path_stddev                   +8.9322         +8.9554             0             0             0             0
BM_sinsp_concatenate_paths_empty_path_cv                       +8.7909         +8.8136             0             0             0             0
BM_sinsp_concatenate_paths_absolute_path_mean                  +0.1073         +0.1073            54            60            54            60
BM_sinsp_concatenate_paths_absolute_path_median                +0.1166         +0.1167            54            60            54            60
BM_sinsp_concatenate_paths_absolute_path_stddev                -0.0980         -0.0983             1             1             1             1
BM_sinsp_concatenate_paths_absolute_path_cv                    -0.1855         -0.1857             0             0             0             0
BM_sinsp_split_container_image_mean                            +0.0290         +0.0290           387           398           387           398
BM_sinsp_split_container_image_median                          +0.0302         +0.0302           386           398           386           398
BM_sinsp_split_container_image_stddev                          -0.3009         -0.3013             2             2             2             2
BM_sinsp_split_container_image_cv                              -0.3206         -0.3209             0             0             0             0

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.69%. Comparing base (f82c686) to head (3b6838a).
Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2146   +/-   ##
=======================================
  Coverage   74.69%   74.69%           
=======================================
  Files         254      254           
  Lines       33502    33502           
  Branches     5746     5714   -32     
=======================================
  Hits        25025    25025           
+ Misses       8477     8446   -31     
- Partials        0       31   +31     

Flag	Coverage Δ
libsinsp	74.69% <ø> (ø)

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[leogr]

Thank you!

/milestone 0.19.0

[poiana]

LGTM label has been added.

Git tree hash: 240ee6c3f790e32450acd50bdc9ddf7b7257d5e7

[FedeDP]

/approve

[poiana]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: FedeDP, federico-sysdig

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