[docs] Use $^ for dependencies in recepies

doc/Makefile

@@ -7,13 +7,16 @@ start:
 	docker pull structurizr/lite
 	docker run --rm -p 8080:8080 -v $(PWD):/usr/local/structurizr structurizr/lite
 
-ci html: dist/index.html dist/manual.html dist/guidebook.html
+ci html: dist/index.html dist/manual.html dist/guidebook.html dist/c-xrefactory.html
 
 dist/index.html: index.adoc
-	asciidoctor index.adoc -D dist
+	asciidoctor $^ -D dist
+
+dist/c-xrefactory.html: c-xrefactory.md
+	asciidoctor $^ -D dist
 
 dist/manual.html: manual.adoc
-	asciidoctor manual.adoc -D dist
+	asciidoctor $^ -D dist
 
 # We convert all references to Structurizr diagrams to PlantUML model references
 dist/guidebook.html: exported_images guidebook.adoc
@@ -23,7 +26,7 @@ dist/guidebook.html: exported_images guidebook.adoc
 # The guidebook is the one and only document in docs b.c. Structurizr likes it that way
 # But to create HTML using asciidoctor we need to concat them all into one document
 guidebook.adoc: docs/*.adoc 00-guidebook.header
-	ls 00-guidebook.header docs/*.adoc | sort | xargs -I {} sh -c 'cat {}; echo ""' > guidebook.adoc
+	ls $^ | sort | xargs -I {} sh -c 'cat {}; echo ""' > guidebook.adoc
 
 # And the diagrams we can export as PUML using Structurizr CLI
 exported_images: