json-autotype 3.x fails it test suite when "cabal" is not in $PATH

[peti]

The test suite has an undeclared dependency on cabal-install, which means that it will fail for users who don't have that tool in $PATH, i.e. because they are working with stack instead:

Running 3 test suites...
Test suite json-autotype-gen-test: RUNNING...
Test suite json-autotype-gen-test: PASS
Test suite logged to: dist/test/json-autotype-3.0.1-json-autotype-gen-test.log
Test suite json-autotype-qc-test: RUNNING...
Test suite json-autotype-qc-test: PASS
Test suite logged to: dist/test/json-autotype-3.0.1-json-autotype-qc-test.log
Test suite json-autotype-examples: RUNNING...
Running json-autotype with executable "cabal" and arguments ["run","--"]
json-autotype-examples: cabal: rawSystem: runInteractiveProcess: exec: does not exist (No such file or directory)
Test suite json-autotype-examples: FAIL
Test suite logged to: dist/test/json-autotype-3.0.1-json-autotype-examples.log
2 of 3 test suites (2 of 3 test cases) passed.

[workshub]

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[mgajda]

Related to #22