Ensure compatibility with a single shared libvips library #178

Job	Run time
Lint	22s
Lint	22s
Functional testing (ubuntu-20.04, 2.1)	25s
Functional testing (ubuntu-20.04, 2.1)	25s
Functional testing (ubuntu-20.04, 2.2)	38s
Functional testing (ubuntu-20.04, 2.2)	38s
Functional testing (ubuntu-20.04, 2.3)	34s
Functional testing (ubuntu-20.04, 2.3)	34s
Functional testing (ubuntu-20.04, 2.4)	37s
Functional testing (ubuntu-20.04, 2.4)	37s
Functional testing (ubuntu-20.04, 2.5)	34s
Functional testing (ubuntu-20.04, 2.5)	34s
Functional testing (ubuntu-20.04, 2.6)	32s
Functional testing (ubuntu-20.04, 2.6)	32s
Functional testing (ubuntu-20.04, 2.7)	39s
Functional testing (ubuntu-20.04, 2.7)	39s
Functional testing (ubuntu-20.04, 3.0)	25s
Functional testing (ubuntu-20.04, 3.0)	25s
Functional testing (ubuntu-20.04, 3.1)	1m 5s
Functional testing (ubuntu-20.04, 3.1)	28s
Functional testing (ubuntu-20.04, 3.2)	23s
Functional testing (ubuntu-20.04, 3.2)	23s
Functional testing (ubuntu-20.04, 3.3)	20s
Functional testing (ubuntu-20.04, 3.3)	20s
Functional testing (ubuntu-20.04, jruby)	53s
Functional testing (ubuntu-20.04, jruby)	1m 1s
	14m 25s

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