[clang] add __uefi__ test for aarch64 & x86_64

Author: RossComputerGuy

clang/test/Preprocessor/init.c

@@ -2742,3 +2742,10 @@
 // RISCV64-LINUX: #define __unix__ 1
 // RISCV64-LINUX: #define linux 1
 // RISCV64-LINUX: #define unix 1
+//
+// RUN: %clang_cc1 -dM -triple=aarch64-unknown-uefi -E < /dev/null | FileCheck -match-full-lines -check-prefix UEFI %s
+// RUN: %clang_cc1 -dM -triple=x86_64-unknown-uefi -E /dev/null | FileCheck -match-full-lines -check-prefix UEFI %s
+//
+// UEFI: #define __uefi 1
+// UEFI: #define __uefi__ 1
+// UEFI: #define uefi 1