Build fails when V is exported

[LocutusOfBorg]

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Hello, in Ubuntu builders, verbose mode is enabled by default with export V=1

this breaks the build of your tool because it does

	$(V)cppo -V COQ:$(COQ_VERSION) -V OCAML:$(OCAML_VERSION) -n -o $@ $^

in Makefile, resulting in a call of something like "1cppo" binary.

Please document the V variable, or remove it if possible (or use a better and longer name?)

thanks

[Lysxia]

OK I will remove it.

[LocutusOfBorg]

Fixed in https://github.com/Lysxia/coq-simple-io/issues/63

[LocutusOfBorg]

I think it was added here https://github.com/Lysxia/coq-simple-io/commit/1ba9d9a483e1f31922bc41bffd8907bc3d6ee85e for no apparent reason?