docs: Check for docbook2man too

diff --git a/docs/Makefile b/docs/Makefile
index 505d74b1b19e4edf8247e90d655ede7597087142..b867e19803e8a0f6ab7f790e0c93c951d32221a4 100644 (file)
--- a/docs/Makefile
+++ b/docs/Makefile
@@ -48,10 +48,14 @@ else
 endif
 
 # Select docbook-to-man tool
-ifeq ($(shell which docbook2x-man), )
+ifneq ($(strip $(shell which docbook2x-man)),)
+       DOCBOOK_TO_MAN=docbook2x-man
+else ifneq ($(strip $(shell which docbook-to-man)),)
        DOCBOOK_TO_MAN=docbook-to-man
+else ifneq ($(strip $(shell which docbook2man)),)
+       DOCBOOK_TO_MAN=docbook2man
 else
-       DOCBOOK_TO_MAN=docbook2x-man
+       $(error Unable to find usable docbook to man conversion tool)
 endif
 
 all: manual $(MANPAGES)