set DIST_SUBDIRS to SUBDIRS in order to prevent failure of make dist

Makefile.am

@@ -63,6 +63,8 @@ if STARPU_BUILD_SC_HYPERVISOR
 SUBDIRS += sc_hypervisor
 endif
 
+DIST_SUBDIRS = $(SUBDIRS)
+
 pkgconfigdir = $(libdir)/pkgconfig
 pkgconfig_DATA = libstarpu.pc starpu-1.0.pc starpu-1.1.pc starpu-1.2.pc starpu-1.3.pc