Fix ocasional failure with parallel install
Gentoo bug: https://bugs.gentoo.org/show_bug.cgi?id=322965
R bug: https://bugs.r-project.org/bugzilla3/show_bug.cgi?id=14505

Patch by Sebastien Fabbro

--- src/include/Makefile.in.orig	2010-06-15 18:18:54.000000000 +0000
+++ src/include/Makefile.in	2010-06-15 18:19:48.000000000 +0000
@@ -81,7 +81,7 @@
 Rmath.h0: $(srcdir)/Rmath.h0.in $(top_builddir)/config.status
 	@cd $(top_builddir) && $(SHELL) ./config.status $(subdir)/$@
 
-install: installdirs install-intl-@USE_INCLUDED_LIBINTL@
+install: $(OBJ_HEADERS) installdirs install-intl-@USE_INCLUDED_LIBINTL@
 	@for d in $(SUBDIRS); do \
 	  (cd $${d} && $(MAKE) $@) || exit 1; \
 	done