Fix incorrect PHONY and add PHONY linter

Makefile

@@ -1,4 +1,11 @@
-none: clean
+SHELL := bash
+.SHELLFLAGS := -eux -o pipefail -c
+.DEFAULT_GOAL := setup
+.DELETE_ON_ERROR:  # If a recipe to build a file exits with an error, delete the file.
+.SUFFIXES:  # Remove the default suffixes which are for compiling C projects.
+.NOTPARALLEL:  # Disable use of parallel subprocesses.
+MAKEFLAGS += --warn-undefined-variables
+MAKEFLAGS += --no-builtin-rules
 
 help:
 	@echo "make test	test Ward"
@@ -15,13 +22,17 @@ help:
 setup:
 	poetry install
 	poetry run pre-commit install
-.PHONY: requirements
+.PHONY: setup
 
 format:
 	poetry run pre-commit run --all
 .PHONY: format
 
-lint: format
+lint-make:
+	python scripts/lint-make
+.PHONY: lint-make
+
+lint: format lint-make
 .PHONY: lint
 
 test:

scripts/lint-make

@@ -0,0 +1,19 @@
+import sys
+
+with open('Makefile', 'rt') as makefile:
+    current_target = None
+    exit_code = 0
+    for line in makefile:
+        words = line.split()
+        if not words:
+            continue
+        elif words[0] == '.PHONY:':
+            phony_target = words[1]
+            if current_target != phony_target:
+                print(f'Error: make target has wrong phony.  Found {phony_target!r}, expected {current_target!r}.')
+                exit_code = 1
+            current_target = None
+        elif words[0].endswith(':'):
+            current_target = words[0][:-1]
+
+sys.exit(exit_code)