cat(1p), true(1p), false(1p): added source files & Makefile

Makefile

@@ -0,0 +1,28 @@
+# Copyright (c) 2023 YAC
+# SPDX-License-Identifier: FSFAP
+#
+# Copying and distribution of this file, with or without modification, are
+# permitted in any medium without royalty provided the copyright notice and this
+# notice are preserved.  This file is offered as-is, without any warranty.
+
+.POSIX:
+
+PREFIX=/usr/local/bin
+
+build: build_dir cat false true
+
+cat: build_dir
+	cc -o build/cat src/cat.c
+
+false: build_dir
+	cc -o build/false src/false.c
+
+true: build_dir
+	cc -o build/true src/true.c
+
+build_dir:
+	mkdir -p build
+
+install: build
+	mkdir -p $(PREFIX)
+	cp -f build/* $(PREFIX)/