build: fix inconsistent quoting in `Makefile` #466

Job	Run time
Build slim tarball	1m 31s
aarch64-linux: with shared libraries	2h 13m 45s
x86_64-linux: with shared libraries	2h 21m 26s
aarch64-darwin: with shared libraries	1h 50m 48s
x86_64-darwin: with shared libraries	2h 28m 49s
	8h 56m 19s

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