disable builtin doc if makeinfo is not found.

doc/handbook/Makefile.am

@@ -85,18 +85,21 @@ if HAS_TEXI2PDF
 arc_handbook_TEXINFOS = ${EXTRA_TEXINFOS} ${EXTRA_DIST}
 endif
 
-pkgdata_DATA=pages.idx ${CMDLINE_FILES}
-
 dvi:
 
+if HAS_MAKEINFO
+pkgdata_DATA=pages.idx ${CMDLINE_FILES}
 all : ${pkgdata_DATA}
 
 echo-pkgdata: 
 	@ echo ${pkgdata_DATA} 
 
-if HAS_MAKEINFO
 .texi.txt:
 	${MAKEINFO} --force --plaintext --fill-column=79 $< -o $@
+
+.PHONY: ${GENERATED_HELP_FILES}
+else
+all :
 endif
 
 pages.texi: ${CMDLINE_HELP_FILES} ${GENERATED_HELP_FILES} 
@@ -125,8 +128,6 @@ pages.idx : ${CMDLINE_HELP_FILES} ${GENERATED_HELP_FILES}
          done; \
         done
 
-.PHONY: ${GENERATED_HELP_FILES}
-
 commands.texi : 
 	(echo "@c %page commands"; \
          echo "@c %title Command list"; \