Allow custom libexec location

To install for different distributions, LIBEXEC_PREFIX can now be set.
It defaults to $(PREFIX)/usr/lib/bees as used in most common
distributions.

Local overrides are possible by setting variables in a "localconf" file
which will be included by the Makefile if it exists.

For some distributions you may want to set it to /usr/libexec or
/usr/libexec/bees.

Makefile

@@ -1,8 +1,12 @@
 PREFIX ?= /
+LIBEXEC_PREFIX ?= $(PREFIX)/usr/lib
 
 MARKDOWN := $(shell which markdown markdown2 markdown_py 2>/dev/null)
 MARKDOWN ?= markdown
 
+# allow local configuration to override above variables
+-include localconf
+
 default all: lib src test README.html
 
 clean: ## Cleanup
@@ -21,6 +25,9 @@ test: ## Run tests
 test: lib src
 	$(MAKE) -C test
 
+scripts/beesd: scripts/beesd.in
+	sed -e's#@LIBEXEC_PREFIX@#$(LIBEXEC_PREFIX)#' -e's#@PREFIX@#$(PREFIX)#' "$<" >"$@"
+
 README.html: README.md
 	$(MARKDOWN) README.md > README.html.new
 	mv -f README.html.new README.html
@@ -28,9 +35,10 @@ README.html: README.md
 install: ## Install bees + libs
 install: lib src test
 	install -Dm644 lib/libcrucible.so $(PREFIX)/usr/lib/libcrucible.so
-	install -Dm755 bin/bees $(PREFIX)/usr/libexec/bees
+	install -Dm755 bin/bees $(LIBEXEC_PREFIX)/bees/bees
 
 install_scripts: ## Install scipts
+install_scripts: scripts/beesd
 	install -Dm755 scripts/beesd $(PREFIX)/usr/sbin/beesd
 	install -Dm644 scripts/beesd.conf.sample $(PREFIX)/etc/bees/beesd.conf.sample
 	install -Dm644 scripts/beesd@.service $(PREFIX)/lib/systemd/system/beesd@.service