Forward --ccache-maxsize CLI arg to obs-build

[dcermak]

Depends on openSUSE/obs-build#970

[codecov]

Codecov Report

Attention: 4 lines in your changes are missing coverage. Please review.

Comparison is base (608fc76) 31.05% compared to head (99055eb) 31.04%.
Report is 6 commits behind head on master.

Files	Patch %	Lines
osc/build.py	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1460      +/-   ##
==========================================
- Coverage   31.05%   31.04%   -0.01%     
==========================================
  Files          49       49              
  Lines       17758    17763       +5     
==========================================
+ Hits         5514     5515       +1     
- Misses      12244    12248       +4     

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[dmach]

The related PR got closed, it makes no sense to keep this one open.