Documentation: implement make target for asciidoc generation

Fixes #3230

Makefile.am

@@ -10,7 +10,9 @@ SUBDIRS = \
 	icinga-app \
 	test \
 	itl \
-	etc
+	etc \
+	docs
+
 #doc
 icinga2docdir = ${docdir}
 icinga2doc_DATA = \
@@ -79,8 +81,3 @@ dist-hook: icinga-version.stamp
 		$(SED) -e 's|^#undef GIT_IS_DIST.*|#define GIT_IS_DIST 1|' \
 			"icinga-version.h" > "$(distdir)/icinga-version.h"; \
 	fi
-
-SRC_DOCS = "./docs"
-
-create-docs:
-	cd $(SRC_DOCS) && $(MAKE)

docs/Makefile.am

@@ -1,7 +1,11 @@
+EXTRA_DIST = \
+	icinga2-config.txt \
+	icinga2-intro.txt
 
-all: create-docs
+icinga2docdir = ${docdir}
+icinga2doc_DATA = \
+	icinga2-config.html \
+	icinga2-intro.html
 
-create-docs:
-	for file in *.txt; \
-	do asciidoc -a toc -a numbered $$file; \
-	done
+%.html: %.txt
+	asciidoc -a toc -a numbered $^