Fix build break on Ubuntu 12.04 with ARM64 changes.

See http://llvm.org/bugs/show_bug.cgi?id=20824 for more details.

Tested:
Ubuntu 12.04 x86_64, gcc-4.9.1-built lldb
Ubuntu 14.04 x86_64, clang-3.5-build lldb

llvm-svn: 217169
diff --git a/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp b/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp
index 416d6a6..bfe8dc9 100644
--- a/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp
+++ b/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp
@@ -65,6 +65,8 @@
 
 #define LLDB_PERSONALITY_GET_CURRENT_SETTINGS  0xffffffff
 
+#define LLDB_PTRACE_NT_ARM_TLS  0x401           // ARM TLS register
+
 // Support hardware breakpoints in case it has not been defined
 #ifndef TRAP_HWBKPT
   #define TRAP_HWBKPT 4
@@ -800,7 +802,7 @@
     {
     case llvm::Triple::aarch64:
     {
-         int regset = NT_ARM_TLS;
+         int regset = LLDB_PTRACE_NT_ARM_TLS;
          struct iovec ioVec;
 
          ioVec.iov_base = m_addr;