Link against gnu-efi from Debian

Adjust EFIINC, LIBDIR and LIBEFI variables in mk/efi.mk to point to the
files installed by Debian's gnu-efi package.
- The LIBDIR path depends on the build hosts' architecture, so the
  DEB_HOST_ARCH variable needs to be exported to determine the correct
  paths.

Forwarded: not-needed

Gbp-Pq: Name 0004-gnu-efi-from-debian.patch

mk/efi.mk

@@ -8,8 +8,15 @@ core = $(topdir)/core
 # gnuefi sets up architecture specifics in ia32 or x86_64 sub directories
 # set up the LIBDIR and EFIINC for building for the appropriate architecture
 GCCOPT := $(call gcc_ok,-fno-stack-protector,)
-EFIINC = $(objdir)/include/efi
-LIBDIR  = $(objdir)/lib
+EFIINC = /usr/include/efi
+LIBDIR  = /usr/lib
+ifeq ($(DEB_HOST_ARCH)/$(ARCH),amd64/i386)
+	LIBDIR  = /usr/lib32
+endif
+ifeq ($(DEB_HOST_ARCH)/$(ARCH),i386/x86_64)
+	LIBDIR  = /usr/lib64
+endif
+
 
 ifeq ($(ARCH),i386)
 	ARCHOPT = -m32 -march=i386
@@ -44,7 +51,7 @@ SFLAGS     = $(GCCOPT) $(GCCWARN) $(ARCHOPT) \
 	     -nostdinc -iwithprefix include \
 	     -I$(com32)/libutil/include -I$(com32)/include -I$(com32)/include/sys $(GPLINCLUDE)
 
-LIBEFI = $(objdir)/lib/libefi.a
+LIBEFI = $(LIBDIR)/libefi.a
 
 $(LIBEFI):
 	@echo Building gnu-efi for $(EFI_SUBARCH)