build-gnu.sh: Let SELinux optional to use it locally without libselinux #3175

Job	Run time
L10n/Build and Test (macos-latest, feat_os_macos)	3m 14s
L10n/Build and Test (windows-latest, feat_os_windows)	4m 36s
L10n/Build and Test (ubuntu-latest, feat_os_unix)	2m 19s
L10n/Fluent Syntax Check	18s
L10n/Clap Error Localization Test	58s
L10n/French Integration Test	58s
L10n/Multi-call Binary Install Test (macos-latest, feat_os_macos)	6m 54s
L10n/Multi-call Binary Install Test (ubuntu-latest, feat_os_unix)	6m 9s
L10n/Locale Support Verification	12m 19s
L10n/Installation Test (Make & Cargo) (macos-latest, feat_os_macos)	8m 13s
L10n/Installation Test (Make & Cargo) (ubuntu-latest, feat_os_unix)	7m 33s
L10n/Locale Embedding - Ls Utility	55s
L10n/Locale Embedding - Multicall Binary	2m 18s
L10n/Locale Embedding - Cat Utility	52s
L10n/Embedded Locale Regression Test	1m 15s
L10n/Locale Embedding - Cargo Install	1m 33s
L10n/Locale Embedding Regression Test	4s
	1h 0m 28s

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