Makefile: Make sure make is invoked with appropriate permissions (#146)

Makefile

@@ -9,6 +9,10 @@ LIB_DIR = $(DESTDIR)$(PREFIX)/lib
 .PHONY: install uninstall help
 
 install:
+ @if test "$(shell id -u)" != 0; then \
+ echo "You are not root, run this target as root please."; \
+ exit 1; \
+ fi
  @install -Dm755 -t "$(DESTDIR)/etc/grub.d/" 41_snapshots-btrfs
  @install -Dm644 -t "$(DESTDIR)/etc/default/grub-btrfs/" config
  @install -Dm644 -t "$(LIB_DIR)/systemd/system/" grub-btrfs.service
@@ -23,6 +27,10 @@ install:
  @install -Dm644 "initramfs/readme.md" "$(SHARE_DIR)/doc/$(PKGNAME)/initramfs-overlayfs.md"
 
 uninstall:
+ @if test "$(shell id -u)" != 0; then \
+ echo "You are not root, run this target as root please."; \
+ exit 1; \
+ fi
  @grub_dirname="$$(grep -oP '^[[:space:]]*GRUB_BTRFS_GRUB_DIRNAME=\K.*' "$(DESTDIR)/etc/default/grub-btrfs/config" | sed "s|\s*#.*||;s|(\s*\(.\+\)\s*)|\1|;s|['\"]||g")"; \
  rm -f "$${grub_dirname:-/boot/grub}/grub-btrfs.cfg"
  @rm -f "$(DESTDIR)/etc/default/grub-btrfs/config"