[Aarch64] Fix linker emulation for Aarch64 big endian

This patch fixes target linker emulation for aarch64 big endian.
aarch64_be_linux is not recognized by gnu ld. The equivalent emulation
mode supported by gnu ld is aarch64linuxb.

Patch by: Bharathi Seshadri

Reviewed by: Peter Smith

Differential Revision: https://reviews.llvm.org/D42930

llvm-svn: 341312

clang/lib/Driver/ToolChains/Gnu.cpp

@@ -237,7 +237,7 @@ static const char *getLDMOption(const llvm::Triple &T, const ArgList &Args) {
   case llvm::Triple::aarch64:
     return "aarch64linux";
   case llvm::Triple::aarch64_be:
-    return "aarch64_be_linux";
+    return "aarch64linuxb";
   case llvm::Triple::arm:
   case llvm::Triple::thumb:
     return "armelf_linux_eabi";

clang/test/Driver/linux-ld.c

@@ -1754,6 +1754,14 @@
 // CHECK-ARMV7EB: "--be8"
 // CHECK-ARMV7EB: "-m" "armelfb_linux_eabi"
 
+// RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
+// RUN:     --target=aarch64_be-unknown-linux \
+// RUN:     --gcc-toolchain="" \
+// RUN:     --sysroot=%S/Inputs/basic_linux_tree \
+// RUN:   | FileCheck --check-prefix=CHECK-AARCH64BE %s
+// CHECK-AARCH64BE: "{{.*}}ld{{(.exe)?}}" "--sysroot=[[SYSROOT:[^"]+]]"
+// CHECK-AARCH64BE: "-m" "aarch64linuxb"
+
 // Check dynamic-linker for musl-libc
 // RUN: %clang %s -### -o %t.o 2>&1 \
 // RUN:     --target=i386-pc-linux-musl \