build: support empty libname flags in `configure.py` #4762

Job	Run time
Build slim tarball	3m 3s
x86_64-linux: with shared libraries	1h 52m 41s
x86_64-darwin: with shared libraries	2h 39m 24s
aarch64-linux: with shared libraries	1h 20m 50s
aarch64-darwin: with shared libraries	1h 23m 18s
	7h 19m 16s

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