lldb-server exec users always /usr/bin/lldb-server. Server is required
for any debugging with lldb which makes it unusable unless default version
package has been installed. Small changes to code and debian/rules allows
a workaround for lldb-server start up.

To use this one needs to add cmake defination during configure. eg
-DDEBIAN_VERSION_SUFFIX=-$(LLVM_VERSION)

Better implementation would be to use /usr/share/llvm-$(VERSION)/bin but 
that change seems to require a big change to the path handling code
which could then break something else.

This probably should have upstream bug but I couldn't find any existing report.

Index: llvm-toolchain-snapshot_4.0~svn286225/CMakeLists.txt
===================================================================
--- llvm-toolchain-snapshot_4.0~svn286225.orig/CMakeLists.txt
+++ llvm-toolchain-snapshot_4.0~svn286225/CMakeLists.txt
@@ -49,6 +49,10 @@ project(LLVM
   ${cmake_3_0_LANGUAGES}
   C CXX ASM)
 
+set(DEBIAN_VERSION_SUFFIX "" CACHE STRING "Versioned program suffix that is required to exec correct subtool.")
+
+add_definitions( -DDEBIAN_VERSION_SUFFIX=\"${DEBIAN_VERSION_SUFFIX}\")
+
 if (NOT CMAKE_BUILD_TYPE AND NOT CMAKE_CONFIGURATION_TYPES)
   message(STATUS "No build type selected, default to Debug")
   set(CMAKE_BUILD_TYPE "Debug" CACHE STRING "Build type (default Debug)" FORCE)
Index: llvm-toolchain-snapshot_4.0~svn286225/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunication.cpp
===================================================================
--- llvm-toolchain-snapshot_4.0~svn286225.orig/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunication.cpp
+++ llvm-toolchain-snapshot_4.0~svn286225/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunication.cpp
@@ -36,10 +36,14 @@
 // Project includes
 #include "ProcessGDBRemoteLog.h"
 
+#ifndef DEBIAN_VERSION_SUFFIX
+#define DEBIAN_VERSION_SUFFIX ""
+#endif
+
 #if defined(__APPLE__)
 #define DEBUGSERVER_BASENAME "debugserver"
 #else
-#define DEBUGSERVER_BASENAME "lldb-server"
+# define DEBUGSERVER_BASENAME    "lldb-server" DEBIAN_VERSION_SUFFIX
 #endif
 
 #if defined(HAVE_LIBCOMPRESSION)