x86: Support building the EFI stub

Add support for building a 32/64-bit EFI stub for x86. This involves
building the startup and relocation code for either i386 or x86_64.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

arch/x86/lib/Makefile

@@ -34,7 +34,7 @@ obj-$(CONFIG_SYS_X86_TSC_TIMER)	+= tsc_timer.o
 obj-$(CONFIG_CMD_ZBOOT)	+= zimage.o
 obj-$(CONFIG_HAVE_FSP) += fsp/
 
-extra-$(CONFIG_USE_PRIVATE_LIBGCC) := lib.a
+extra-$(CONFIG_USE_PRIVATE_LIBGCC) += lib.a
 
 NORMAL_LIBGCC = $(shell $(CC) $(PLATFORM_CPPFLAGS) -print-libgcc-file-name)
 OBJCOPYFLAGS := --prefix-symbols=__normal_

arch/x86/lib/efi/Makefile

@@ -0,0 +1,24 @@
+#
+# (C) Copyright 2002-2006
+# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+
+obj-$(CONFIG_EFI_APP) += crt0-efi-ia32.o reloc_ia32.o
+
+ifneq ($(CONFIG_EFI_STUB),)
+
+CFLAGS_REMOVE_reloc_ia32.o += -mregparm=3
+CFLAGS_reloc_ia32.o += -fpic -fshort-wchar
+
+# When building for 64-bit we must remove the i386-specific flags
+CFLAGS_REMOVE_reloc_x86_64.o += -mregparm=3 -march=i386 -m32
+CFLAGS_reloc_x86_64.o += -fpic -fshort-wchar
+
+AFLAGS_REMOVE_crt0-efi-x86_64.o += -mregparm=3 -march=i386 -m32
+AFLAGS_crt0-efi-x86_64.o += -fpic -fshort-wchar
+
+extra-$(CONFIG_EFI_STUB_32BIT) += crt0-efi-ia32.o reloc_ia32.o
+extra-$(CONFIG_EFI_STUB_64BIT) += crt0-efi-x86_64.o reloc_x86_64.o
+endif