Don't use experimental cabal-doctest

- Pin doctest-0.24.3

Author: philderbeast

Makefile

@@ -5,7 +5,7 @@
 CABALBUILD := cabal build
 CABALRUN   := cabal run
 
-DOCTEST := cabal doctest
+DOCTEST := cabal repl --with-compiler=doctest --build-depends=QuickCheck --verbose=0 --repl-options='-w -Wdefault -Wno-inconsistent-flags'
 
 # default rules
 
@@ -157,9 +157,12 @@ doctest: ## Run doctests.
 	cd cabal-install-solver && $(DOCTEST)
 	cd cabal-install && $(DOCTEST)
 
+# We don't use the cabal-doctest external command but we install it anyway along
+# with doctest.
+# SEE: https://github.com/haskell/cabal/issues/11493
 .PHONY: doctest-install
 doctest-install: ## Install doctest tool needed for running doctests.
-	cabal install doctest --overwrite-policy=always --ignore-project --flag cabal-doctest
+	cabal install doctest-0.24.3 --overwrite-policy=always --ignore-project --flag cabal-doctest
 
 # tests