Makefile: fix MANDIR, fix for macOS

- MANDIR was not a directory before; now it is

- macOS has no "root" group, and -g/-o are rarely needed anyway

  - hat tip to osmcode/libosmium#18

- fairly-recent macOS (Mojave) still does not have 'install -D' so do
  'install -d' explicitly for the parent directories, particularly for
  'man8', since that probably won't exist in most people's
  /usr/local/share/man to begin with

Makefile

@@ -1,11 +1,10 @@
 # Makefile for symlinks
 CC      = gcc
+# append options like `-o owner -g group` here if desired
 INSTALL = install
 CFLAGS += $(shell getconf LFS_CFLAGS 2>/dev/null)
-OWNER   = root
-GROUP   = root
 PREFIX ?= /usr/local
-MANDIR ?= $(PREFIX)/share/man/man8/symlinks.8
+MANDIR ?= $(PREFIX)/share/man/man8
 BINDIR ?= $(PREFIX)/bin
 
 
@@ -16,8 +15,10 @@ symlinks: symlinks.c
 	$(CC) -Wall -Wstrict-prototypes -O2 $(CFLAGS) -o symlinks symlinks.c
 
 install: all symlinks.8
-	$(INSTALL) -c -o $(OWNER) -g $(GROUP) -m 755 symlinks $(BINDIR)
-	$(INSTALL) -c -o $(OWNER) -g $(GROUP) -m 644 symlinks.8 $(MANDIR)
+	$(INSTALL) -d $(BINDIR)
+	$(INSTALL) -m 755 symlinks $(BINDIR)
+	$(INSTALL) -d $(MANDIR)
+	$(INSTALL) -m 644 symlinks.8 $(MANDIR)
 
 .PHONY: clean
 clean: