ci: Read build matrix JSON explicitly #650

Job	Run time
Settings / settings	2s
Lint / Lint	14s
Official Docker image / Build	11m 33s
Build and test / Matrix configuration	5s
Build docs / Build docs	38s
Test Linux distros / Matrix configuration	4s
Build and test / linux x64 Debug static	9m 54s
Build and test / linux x64 Debug shared	9m 29s
Build and test / linux x64 Release static	13m 43s
Build and test / linux x64 Release shared	10m 44s
Build and test / osx x64 Debug static	27m 50s
Test Linux distros / Alpine	12m 39s
Build and test / osx x64 Debug shared	27m 0s
Test Linux distros / ArchLinux	11m 53s
Build and test / osx x64 Release static	10m 35s
Test Linux distros / CentOS	10m 52s
Build and test / osx x64 Release shared	14m 44s
Test Linux distros / Debian	12m 3s
Build and test / osx arm64 Debug static	18m 49s
Test Linux distros / Fedora	10m 6s
Build and test / osx arm64 Debug shared	17m 36s
Test Linux distros / OpenSUSE	10m 52s
Build and test / osx arm64 Release static	10m 3s
Test Linux distros / Ubuntu	9m 47s
Build and test / osx arm64 Release shared	7m 15s
Build and test / win x64 Debug static	14m 22s
Build and test / win x64 Debug shared	14m 11s
Build and test / win x64 Release static	17m 54s
Build and test / win x64 Release shared	16m 50s
Build and test / linux arm64 Debug static	11m 11s
Build and test / linux arm64 Debug shared	11m 18s
Build and test / linux arm64 Release static	12m 30s
Build and test / linux arm64 Release shared	12m 13s
	6h 18m 59s

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