fix code in order to support cmake unity builds

[tnixeu]

What type of PR is this? (check all applicable)

• Refactor
• Feature
• Bug Fix
• Optimization
• Documentation Update
• Other: Replace this with a description of the type of this PR

Description

I tired building polybar with CMAKE_UNITY_BUILD":"ON" and the build failed.

The #pragma once in base.inl is needed because it is included multiple times when passed to the compiler.

I am not exactly sure why the changes in encoder.cpp are needed. However, both gcc and clang fail. The variable header could be renamed Instead of adding polybar:: to ipc::header. However, this would change more lines.

Both changes should have no impact on the runtime ore a normal build.

Related Issues & Documents

Documentation (check all applicable)

• This PR requires changes to the Wiki documentation (describe the changes)
• This PR requires changes to the documentation inside the git repo (please add them to the PR).
• Does not require documentation changes

[patrick96]

Dang, I didn't know about unity builds, this makes compiling around twice as fast on my machine 😃.

(It will probably affect the performance of ccache though)

[codecov]

Codecov Report

Merging #2851 (8a7f7b0) into master (10cdec3) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #2851   +/-   ##
=======================================
  Coverage   13.17%   13.17%           
=======================================
  Files         162      162           
  Lines       11509    11509           
=======================================
  Hits         1516     1516           
  Misses       9993     9993           

Flag	Coverage Δ
unittests	13.17% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
include/modules/meta/base.inl	0.00% <ø> (ø)
src/ipc/encoder.cpp	85.71% <100.00%> (ø)

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[tnixeu]

Dang, I didn't know about unity builds, this makes compiling around twice as fast on my machine smiley.

(It will probably affect the performance of ccache though)

This surprised me as well, when I first learnt about it. One drawback is, that compiling small changes can take longer because more code is compiled again as well.

[patrick96]

Thanks!