Provide a `make uninstall` target

Currently there is no clean way to uninstall GHC built from source. The makefiles should provide an uninstall target that allows this.

Trac metadata

Trac field	Value
Version	8.0.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture

changed weight to 5

added Tbug Trac import labels

Trac metadata

Trac field	Value
Component	Compiler → Build System

closed

Trac metadata

Trac field	Value
Resolution	Unresolved → ResolvedDuplicate
Related	- → #11191

The new Hadrian build system has been merged. Relabeling the tickets concerning the legacy make build system to prevent confusion.

Trac metadata

Trac field	Value
Component	Build System → Build System (make)

added Pnormal label