GHC_PACKAGE_PATH should be more lenient for empty paths

Consider a working GHC_PACKAGE_PATH=foo:bar:baz:.

It is not uncommon that we would want to append som extra vars later which might possibly be empty, perhaps resulting in GHC_PACKAGE_PATH=foo:bar:baz::qux:. Unfortunately, due to the :: GHC tries to looking for a package at the empty path and shows the usual error about not being able to find the package. This forces the user to set up various safeguards (such as ${GHC_PACKAGE_PATH:+:} bashism) at the inital binding location.

It'd be great if GHC would simply skip over empty paths.

Trac metadata

Trac field	Value
Version	7.8.3
Type	FeatureRequest
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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