Portability: remove explicit check for libdl #241

Job	Run time
functionality-tests	18m 18s
source-maintenance-tests	2m 47s
CodeQL-tests	34m 58s
build-tests(ubuntu-22.04,gcc,default)	6m 31s
build-tests(ubuntu-22.04,gcc,minimal)	4m 34s
build-tests(ubuntu-22.04,gcc,maximus)	7m 14s
build-tests(ubuntu-22.04,clang,default)	7m 23s
build-tests(ubuntu-22.04,clang,minimal)	5m 36s
build-tests(ubuntu-22.04,clang,maximus)	8m 31s
	1h 35m 52s

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