Out-of-tree building of perl modules.

configure.ac

@@ -341,7 +341,7 @@ AC_SUBST(dynlib_suffix)
 
 # Do we have GNU tar?
 AC_MSG_CHECKING([if you have a recent GNU tar])
-if $tar --version 2> /dev/null | grep -q GNU && tar cvf /dev/null --warning=no-timestamp ./configure > /dev/null; then
+if $tar --version 2> /dev/null | grep -q GNU && tar cvf /dev/null --warning=no-timestamp ./config.log > /dev/null; then
     AC_MSG_RESULT(yes)
     tarFlags="--warning=no-timestamp"
 else

perl/Makefile.am

@@ -26,6 +26,7 @@ AM_CXXFLAGS = \
   -D_FILE_OFFSET_BITS=64
 
 lib/Nix/Store.cc: lib/Nix/Store.xs
+	$(INSTALL) -d lib/Nix
 	xsubpp $^ -output $@
 
 else