[PATCH v2] x86/boot: Fix include paths for 32bit objects

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Most of Xen is build using -nostdinc and a fully specified include path.
However, the makefile line:

  $(head-bin-objs): XEN_CFLAGS := $(CFLAGS_x86_32) -fpic

discards XEN_CFLAGS and replaces them with CFLAGS_x86_32.

Reinstate -nostdinc, and copy all -I (and -Wa,-I) arguments from XEN_CFLAGS.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Anthony PERARD <anthony.perard@xxxxxxxxxx>

v2:
 * Copy all -I from XEN_CFLAGS

https://cirrus-ci.com/build/6740464739549184

Note that this misses the overall '-include ./include/xen/config.h' but it was
missing before as well.
---
 xen/arch/x86/boot/Makefile | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/xen/arch/x86/boot/Makefile b/xen/arch/x86/boot/Makefile
index 03d8ce3a9e48..1ec2b123305d 100644
--- a/xen/arch/x86/boot/Makefile
+++ b/xen/arch/x86/boot/Makefile
@@ -14,10 +14,7 @@ $(obj)/head.o: $(head-bin-objs:.o=.bin)
 CFLAGS_x86_32 := $(subst -m64,-m32 -march=i686,$(XEN_TREEWIDE_CFLAGS))
 $(call cc-options-add,CFLAGS_x86_32,CC,$(EMBEDDED_EXTRA_CFLAGS))
 CFLAGS_x86_32 += -Werror -fno-builtin -g0 -msoft-float
-ifneq ($(abs_objtree),$(abs_srctree))
-CFLAGS_x86_32 += -I$(objtree)/include
-endif
-CFLAGS_x86_32 += -I$(srctree)/include
+CFLAGS_x86_32 += -nostdinc $(filter -I% -Wa$(comma)-I%,$(XEN_CFLAGS))
 
 # override for 32bit binaries
 $(head-bin-objs): CFLAGS_stack_boundary :=
-- 
2.39.2