Remove LLDB_DEFAULT_SHELL #define, and determine this at runtime.

Differential Revision: http://reviews.llvm.org/D5805
Reviewed by: Greg Clayton

llvm-svn: 220217
diff --git a/lldb/source/Interpreter/CommandInterpreter.cpp b/lldb/source/Interpreter/CommandInterpreter.cpp
index b281bf1..9097ab0 100644
--- a/lldb/source/Interpreter/CommandInterpreter.cpp
+++ b/lldb/source/Interpreter/CommandInterpreter.cpp
@@ -339,7 +339,11 @@
 #if defined (__arm__) || defined (__arm64__) || defined (__aarch64__)
         ProcessAliasOptionsArgs (cmd_obj_sp, "--", alias_arguments_vector_sp);
 #else
-        ProcessAliasOptionsArgs (cmd_obj_sp, "--shell=" LLDB_DEFAULT_SHELL " --", alias_arguments_vector_sp);
+        std::string shell_option;
+        shell_option.append("--shell=");
+        shell_option.append(HostInfo::GetDefaultShell().GetPath());
+        shell_option.append(" --");
+        ProcessAliasOptionsArgs (cmd_obj_sp, shell_option.c_str(), alias_arguments_vector_sp);
 #endif
         AddAlias ("r", cmd_obj_sp);
         AddAlias ("run", cmd_obj_sp);