Fix VPATH build

When trying to build shadow in a different directory I stumbled upon few
issues, this commit aims to fix all of them:

- The `subid.h` file is generated and hence in the build directory and
	not in the source directory, so use `$(builddir)` instead of
	`$(srcdir)`.

- Using `$<` instead of filenames utilises autotools to locate the files
  in either the source or build directory automatically.

- `xsltproc` needs to access the files in login.defs.d in either the
  source directory or the symlink in a language subdirectory, but it
	does not interpret the `--path` as prefix of the entity path, but
	rather a path under which to locate the basename of the entity
	from the XML file.  So specify the whole path to login.defs.d.

- The above point could be used to make the symlinks of login.defs.d
  and entity path specifications in the XMLs obsolete, but I trying
	not to propose possibly disrupting patches, so for the sake of
	simplicity just specify `$(srcdir)` when creating the symlink.

Signed-off-by: Martin Kletzander <mkletzan@redhat.com>

man/Makefile.am

@@ -206,9 +206,9 @@ if !ENABLE_SUBIDS
 EXTRA_DIST += $(man_subids)
 endif
 
-generate_mans.deps: *.xml
+generate_mans.deps: $(man_XMANS)
 	echo "# This file is generated" > $@
-	awk 'BEGIN{FS="\"";} /^<!ENTITY .* * SYSTEM ".*">$$/{ f=FILENAME; sub(/.xml/,"",f); print "man" substr(f, length (f)) "/" f ": " $$2 }' $(man_XMANS) >> $@
+	awk 'BEGIN{FS="\"";} /^<!ENTITY .* * SYSTEM ".*">$$/{ f=FILENAME; sub(/.xml/,"",f); print "man" substr(f, length (f)) "/" f ": " $$2 }' $< >> $@
 
 if ENABLE_REGENERATE_MAN
 

man/generate_mans.mak

@@ -45,6 +45,7 @@ man1/% man3/% man5/% man8/%: %.xml-config Makefile config.xml
 	            --stringparam "man.output.base.dir" "" \
 	            --stringparam vendordir "$(VENDORDIR)" \
 	            --param "man.output.in.separate.dir" "1" \
+	            --path "$(srcdir)/login.defs.d" \
 	            -nonet $(top_builddir)/man/shadow-man.xsl $<
 
 clean-local:

man/generate_translations.mak

@@ -6,10 +6,10 @@ config.xml: ../config.xml.in
 	cp ../config.xml $@
 
 messages.mo: ../po/$(LANG).po
-	msgfmt ../po/$(LANG).po -o messages.mo
+	msgfmt $< -o messages.mo
 
 login.defs.d:
-	ln -sf ../login.defs.d login.defs.d
+	ln -sf $(srcdir)/../login.defs.d login.defs.d
 
 %.xml: ../%.xml messages.mo login.defs.d
 	if grep -q SHADOW-CONFIG-HERE $< ; then \

src/Makefile.am

@@ -188,7 +188,7 @@ getsubids_CPPFLAGS = \
 	-I$(top_srcdir)/lib \
 	-I$(top_srcdir)/libmisc \
 	-I$(top_srcdir) \
-	-I$(top_srcdir)/libsubid
+	-I$(top_builddir)/libsubid
 
 get_subid_owners_LDADD = \
 	$(top_builddir)/lib/libshadow.la \
@@ -200,13 +200,13 @@ get_subid_owners_CPPFLAGS = \
 	-I$(top_srcdir)/lib \
 	-I$(top_srcdir)/libmisc \
 	-I$(top_srcdir) \
-	-I$(top_srcdir)/libsubid
+	-I$(top_builddir)/libsubid
 
 new_subid_range_CPPFLAGS = \
 	-I$(top_srcdir)/lib \
 	-I$(top_srcdir)/libmisc \
 	-I$(top_srcdir) \
-	-I$(top_srcdir)/libsubid
+	-I$(top_builddir)/libsubid
 
 new_subid_range_LDADD = \
 	$(top_builddir)/lib/libshadow.la \
@@ -218,7 +218,7 @@ free_subid_range_CPPFLAGS = \
 	-I$(top_srcdir)/lib \
 	-I$(top_srcdir)/libmisc \
 	-I$(top_srcdir) \
-	-I$(top_srcdir)/libsubid
+	-I$(top_builddir)/libsubid
 
 free_subid_range_LDADD = \
 	$(top_builddir)/lib/libshadow.la \