x86: Update compile/link flags to support 64-bit U-Boot

Update config.mk settings to support both 32-bit and 64-bit U-Boot.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/x86/config.mk b/arch/x86/config.mk
index 1697dca..74b87ce 100644
--- a/arch/x86/config.mk
+++ b/arch/x86/config.mk
@@ -15,11 +15,25 @@
 
 PLATFORM_CPPFLAGS += $(PF_CPPFLAGS_X86)
 PLATFORM_CPPFLAGS += -fno-dwarf2-cfi-asm
+
+ifdef CONFIG_SPL_BUILD
+IS_32BIT := y
+else
+ifndef CONFIG_X86_64
+IS_32BIT := y
+endif
+endif
+
+ifeq ($(IS_32BIT),y)
 PLATFORM_CPPFLAGS += -march=i386 -m32
+else
+PLATFORM_CPPFLAGS += $(if $(CONFIG_SPL_BUILD),,-fpic) -fno-common
+endif
 
 PLATFORM_RELFLAGS += -ffunction-sections -fvisibility=hidden
 
-PLATFORM_LDFLAGS += -Bsymbolic -Bsymbolic-functions -m elf_i386
+PLATFORM_LDFLAGS += -Bsymbolic -Bsymbolic-functions
+PLATFORM_LDFLAGS += -m $(if $(IS_32BIT),elf_i386,elf_x86_64)
 
 LDFLAGS_FINAL += --wrap=__divdi3 --wrap=__udivdi3
 LDFLAGS_FINAL += --wrap=__moddi3 --wrap=__umoddi3
@@ -31,7 +45,9 @@
 OBJCOPYFLAGS_EFI := -j .text -j .sdata -j .data -j .dynamic -j .dynsym \
 	-j .rel -j .rela -j .reloc
 
+ifeq ($(IS_32BIT),y)
 CFLAGS_NON_EFI := -mregparm=3
+endif
 CFLAGS_EFI := -fpic -fshort-wchar
 
 ifeq ($(CONFIG_EFI_STUB_64BIT),)
@@ -62,10 +78,20 @@
 
 PLATFORM_CPPFLAGS += $(CFLAGS_NON_EFI)
 PLATFORM_LDFLAGS += --emit-relocs
-LDFLAGS_FINAL += --gc-sections -pie
+LDFLAGS_FINAL += --gc-sections $(if $(CONFIG_SPL_BUILD),,-pie)
 
 endif
 
+ifdef CONFIG_X86_64
+ifndef CONFIG_SPL_BUILD
+PLATFORM_CPPFLAGS += -D__x86_64__
+else
+PLATFORM_CPPFLAGS += -D__I386__
+endif
+else
+PLATFORM_CPPFLAGS += -D__I386__
+endif
+
 ifneq ($(CONFIG_EFI_STUB)$(CONFIG_CMD_BOOTEFI_HELLO_COMPILE),)
 
 ifneq ($(CONFIG_EFI_STUB_64BIT),)