Fix race condition when installing init binary

The old situation led to errors when building the Debian package with
more than one thread.

Makefile.am

@@ -1,6 +1,6 @@
 AM_CPPFLAGS = -Wall -Wextra
 
-pkglibexec_PROGRAMS = tiny_initramfs
+noinst_PROGRAMS = tiny_initramfs
 
 tiny_initramfs_SOURCES    = tiny_initramfs.c io.c fstab.c mount.c log.c devices.c util.c
 if ENABLE_NFS4
@@ -11,12 +11,19 @@ tiny_initramfs_LDFLAGS    = -static
 
 EXTRA_DIST = README.md tiny_initramfs.h nfs4.h
 
+installdirs-local:
+	$(MKDIR_P) "$(DESTDIR)$(pkglibexecdir)"
+
 if HAVE_VARIANT
-install-exec-hook:
-	cd $(DESTDIR)$(pkglibexecdir) && \
-		mv -f tiny_initramfs init-@VARIANT@
+install-exec-local:
+	$(MKDIR_P) "$(DESTDIR)$(pkglibexecdir)"
+	$(INSTALL_PROGRAM_ENV) $(INSTALL_PROGRAM) tiny_initramfs$(EXEEXT) "$(DESTDIR)$(pkglibexecdir)/init-@VARIANT@$(EXEEXT)"
+uninstall-local:
+	rm -f "$(DESTDIR)$(pkglibexecdir)/init-@VARIANT@$(EXEEXT)"
 else
-install-exec-hook:
-	cd $(DESTDIR)$(pkglibexecdir) && \
-		mv -f tiny_initramfs init
+install-exec-local:
+	$(MKDIR_P) "$(DESTDIR)$(pkglibexecdir)"
+	$(INSTALL_PROGRAM_ENV) $(INSTALL_PROGRAM) tiny_initramfs$(EXEEXT) "$(DESTDIR)$(pkglibexecdir)/init$(EXEEXT)"
+uninstall-local:
+	rm -f "$(DESTDIR)$(pkglibexecdir)/init$(EXEEXT)"
 endif