Build userland headers and add them to the front of the system include path

This fixes a build failure in tools/hv when the installed
linux-libc-dev is too old.

debian/bin/genorig.py

@@ -142,8 +142,10 @@ class Main(object):
                 'Makefile',
                 'arch/*/include/',
                 'arch/*/Makefile',
+                'arch/x86/syscalls/',
                 'arch/x86/lib/memcpy_64.S',
                 'arch/x86/lib/memset_64.S',
+                'arch/x86/tools/',
                 'include/',
                 'lib/hweight.c',
                 'lib/rbtree.c',

debian/build/Makefile

@@ -9,3 +9,13 @@ SUBDIRS = \
 OUTDIR = .
 
 include Makefile.inc
+
+# Build userland headers first
+unexport VERSION
+all-local:
+	$(MAKE) -C $(top_srcdir) O=$(CURDIR)/out \
+		INSTALL_HDR_PATH=$(CURDIR) headers_install
+all-recursive: all-local
+
+clean-local::
+	rm -rf generated include out

debian/build/Makefile.inc

@@ -7,7 +7,8 @@ SHELL = /bin/sh -e
 CC = gcc
 CXX = g++
 CFLAGS ?= -O2 -Wall
-CPPFLAGS = -I$(top_srcdir)/$(OUTDIR) -I$(top_srcdir)/debian/build/$(OUTDIR)
+CPPFLAGS = -I$(top_srcdir)/$(OUTDIR) -I$(top_srcdir)/debian/build/$(OUTDIR) \
+	-isystem $(top_srcdir)/debian/build/include
 CXXFLAGS = $(CFLAGS)
 
 all: all-local all-recursive