If DESTDIR is defined in d/rules, embedded LLVM installation would break.
If DESTDIR is not defined in d/rules, embedded LLVM installation works, but Julia breaks.
This hack makes both LLVM and Julia happy.

Index: julia/Makefile
===================================================================
--- julia.orig/Makefile
+++ julia/Makefile
@@ -328,6 +328,7 @@ JL_PRIVATE_LIBS-0 += libgfortran libgcc_
 endif
 
 
+override DESTDIR=./debian/tmp/
 install: $(build_depsbindir)/stringreplace $(BUILDROOT)/doc/_build/html/en/index.html
 	@$(MAKE) $(QUIET_MAKE) all
 	@for subdir in $(bindir) $(datarootdir)/julia/stdlib/$(VERSDIR) $(docdir) $(man1dir) $(includedir)/julia $(libdir) $(private_libdir) $(sysconfdir); do \