efi_loader: correctly identify binary name

Only on the sandbox the default EFI binary name (e.g. BOOTX64.EFI) must
match the host architecture.

In all other cases we must use the target architecture.

Use #elif where appropriate.

Reported-by: Vagrant Cascadian <vagrant@reproducible-builds.org>
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/include/efi_default_filename.h b/include/efi_default_filename.h
index 13b9de8..7793298 100644
--- a/include/efi_default_filename.h
+++ b/include/efi_default_filename.h
@@ -5,6 +5,7 @@
  * file name is defined in this include.
  *
  * Copyright (c) 2022, Heinrich Schuchardt <xypron.glpk@gmx.de>
+ * Copyright (c) 2022, Linaro Limited
  */
 
 #ifndef _EFI_DEFAULT_FILENAME_H
@@ -14,32 +15,42 @@
 
 #undef BOOTEFI_NAME
 
+#ifdef CONFIG_SANDBOX
+
 #if HOST_ARCH == HOST_ARCH_X86_64
 #define BOOTEFI_NAME "BOOTX64.EFI"
-#endif
-
-#if HOST_ARCH == HOST_ARCH_X86
+#elif HOST_ARCH == HOST_ARCH_X86
 #define BOOTEFI_NAME "BOOTIA32.EFI"
-#endif
-
-#if HOST_ARCH == HOST_ARCH_AARCH64
+#elif HOST_ARCH == HOST_ARCH_AARCH64
 #define BOOTEFI_NAME "BOOTAA64.EFI"
-#endif
-
-#if HOST_ARCH == HOST_ARCH_ARM
+#elif HOST_ARCH == HOST_ARCH_ARM
 #define BOOTEFI_NAME "BOOTARM.EFI"
-#endif
-
-#if HOST_ARCH == HOST_ARCH_RISCV32
+#elif HOST_ARCH == HOST_ARCH_RISCV32
 #define BOOTEFI_NAME "BOOTRISCV32.EFI"
+#elif HOST_ARCH == HOST_ARCH_RISCV64
+#define BOOTEFI_NAME "BOOTRISCV64.EFI"
+#else
+#error Unsupported UEFI architecture
 #endif
 
-#if HOST_ARCH == HOST_ARCH_RISCV64
+#else
+
+#if defined(CONFIG_ARM64)
+#define BOOTEFI_NAME "BOOTAA64.EFI"
+#elif defined(CONFIG_ARM)
+#define BOOTEFI_NAME "BOOTARM.EFI"
+#elif defined(CONFIG_X86_64)
+#define BOOTEFI_NAME "BOOTX64.EFI"
+#elif defined(CONFIG_X86)
+#define BOOTEFI_NAME "BOOTIA32.EFI"
+#elif defined(CONFIG_ARCH_RV32I)
+#define BOOTEFI_NAME "BOOTRISCV32.EFI"
+#elif defined(CONFIG_ARCH_RV64I)
 #define BOOTEFI_NAME "BOOTRISCV64.EFI"
+#else
+#error Unsupported UEFI architecture
 #endif
 
-#ifndef BOOTEFI_NAME
-#error Unsupported UEFI architecture
 #endif
 
 #endif