Introduce cabal.project.local.example.

Makefile

@@ -70,7 +70,7 @@ full-clean: clean
 .PHONY: clean
 clean:
 	cabal clean
-	-rm -rf dist
+	-rm -rf dist .ghc.environment # cabal-v2 does not use these any more, so they shouldn't be there in the first place.
 	-rm -f "bill-of-materials.$(HELM_SEMVER).json"
 
 .PHONY: clean-hint
@@ -83,14 +83,18 @@ clean-hint:
 
 .PHONY: cabal.project.local
 cabal.project.local:
-	cp ./hack/bin/cabal.project.local.template ./cabal.project.local
+	cp ./hack/cabal.project.local.template ./cabal.project.local
 
 # Usage: make c package=brig test=1
 .PHONY: c
 c: treefmt c-fast
 
 .PHONY: c
 c-fast:
+	if [ ! -e "cabal.project.local" ]; then \
+	  echo "'cabal.project.local' not found. please run 'make cabal.project.local' and tweak the output to your liking."
+	  exit 1; \
+	fi
 	cabal build $(WIRE_CABAL_BUILD_OPTIONS) $(package) || ( make clean-hint; false )
 ifeq ($(test), 1)
 	./hack/bin/cabal-run-tests.sh $(package) $(testargs)

hack/cabal.project.local.template

@@ -0,0 +1,12 @@
+-- disable profilling. if you are using hls/lsp, you probably want to
+-- enable this. same as `ghc-options: -fwrite-ide-info`.
+profiling: False
+profiling-detail: late
+
+-- .ghc.environment is not used in .cabal-v2 and may conflict with hls.
+write-ghc-environment-files: never
+
+-- disable optimization. very important for dev machines. implies `ghc-options: -O0`.
+optimization: False
+
+test-show-details: direct