Makefile.am, docs/Makefile.am: use abs_top_builddir for wrapper rules

Signed-off-by: Jim Klimov <jimklimov+nut@gmail.com>

Makefile.am

@@ -177,12 +177,12 @@ spellcheck spellcheck-interactive:
 doc spellcheck-sortdict \
 all-docs check-docs \
 man all-man man-man check-man man-html all-html:
-	+cd $(builddir)/docs && $(MAKE) $(AM_MAKEFLAGS) -s $(abs_top_builddir)/docs/.prep-src-docs
-	+cd $(builddir)/docs/man && $(MAKE) $(AM_MAKEFLAGS) -s $(abs_top_builddir)/docs/man/.prep-src-docs
-	+cd $(builddir)/docs && $(MAKE) $(AM_MAKEFLAGS) $@
+	+cd $(abs_top_builddir)/docs && $(MAKE) $(AM_MAKEFLAGS) -s $(abs_top_builddir)/docs/.prep-src-docs
+	+cd $(abs_top_builddir)/docs/man && $(MAKE) $(AM_MAKEFLAGS) -s $(abs_top_builddir)/docs/man/.prep-src-docs
+	+cd $(abs_top_builddir)/docs && $(MAKE) $(AM_MAKEFLAGS) $@
 
 INSTALL.nut UPGRADING NEWS README:
-	+cd $(builddir)/docs && $(MAKE) $(AM_MAKEFLAGS) ../$(@F).adoc-parsed && cp -f ../$(@F).adoc-parsed ../$(@F)
+	+cd $(abs_top_builddir)/docs && $(MAKE) $(AM_MAKEFLAGS) ../$(@F).adoc-parsed && cp -f ../$(@F).adoc-parsed ../$(@F)
 
 # Workarounds for https://github.com/github/markup/issues/1095
 # require direct definition of our attributes in each source

docs/Makefile.am

@@ -186,10 +186,10 @@ check-html-chunked: $(ASCIIDOC_HTML_CHUNKED)
 # chosen during configure script execution. The "all-man" and "all-html"
 # rules build everything documented.
 check-man all-man man-man all-html html-man:
-	+cd $(top_builddir)/docs/man/ && $(MAKE) $(AM_MAKEFLAGS) -f Makefile $@
+	+cd $(abs_top_builddir)/docs/man/ && $(MAKE) $(AM_MAKEFLAGS) -f Makefile $@
 
 man:
-	+cd $(top_builddir)/docs/man/ && $(MAKE) $(AM_MAKEFLAGS) -f Makefile all
+	+cd $(abs_top_builddir)/docs/man/ && $(MAKE) $(AM_MAKEFLAGS) -f Makefile all
 
 CLEANFILES = *.xml *.html *.pdf *-spellchecked docbook-xsl.css docinfo.xml.in.tmp
 CLEANFILES += $(top_builddir)/INSTALL.nut $(top_builddir)/UPGRADING $(top_builddir)/NEWS $(top_builddir)/ChangeLog.adoc $(top_builddir)/README