Add explicit dependency on headers to swig wrapper (cmake build)

[emaste]

Summary

So that we will rerun swig automatically to avoid the issue in llvm.org/pr23686

[sivachandra]

I am not really familiar with CMake style.

scripts/CMakeLists.txt

 set(LLVM_NO_RTTI 1)
 
 file(GLOB SWIG_INTERFACES interface/*.i)
 file(GLOB_RECURSE SWIG_SOURCES *.swig)
+set(SWIG_HEADERS
+  ${LLDB_SOURCE_DIR}/include/lldb/API/SBDefines.h
+  ${LLDB_SOURCE_DIR}/include/lldb/lldb-defines.h
+  ${LLDB_SOURCE_DIR}/include/lldb/lldb-enumerations.h
+  ${LLDB_SOURCE_DIR}/include/lldb/lldb-forward.h
+  ${LLDB_SOURCE_DIR}/include/lldb/lldb-types.h
+  ${LLDB_SOURCE_DIR}/include/lldb/lldb-versioning.h
+)
 
 if ( LLDB_ENABLE_PYTHON_SCRIPTS_SWIG_API_GENERATION )
   find_package(SWIG REQUIRED)
   add_custom_command(
     OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/LLDBWrapPython.cpp
     DEPENDS ${SWIG_SOURCES}
     DEPENDS ${SWIG_INTERFACES}
+    DEPENDS ${SWIG_HEADERS}
     DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/buildSwigWrapperClasses.py
     COMMAND ${PYTHON_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/buildSwigWrapperClasses.py "--srcRoot=${LLDB_SOURCE_DIR}" "--targetDir=${CMAKE_CURRENT_BINARY_DIR}" "--cfgBldDir=${CMAKE_CURRENT_BINARY_DIR}" "--prefix=${CMAKE_BINARY_DIR}" "--swigExecutable=${SWIG_EXECUTABLE}" -m
     COMMENT "Python script building LLDB Python wrapper")  
   set_source_files_properties(${CMAKE_CURRENT_BINARY_DIR}/LLDBWrapPython.cpp PROPERTIES GENERATED 1)
 
   add_custom_target(swig_wrapper ALL
     DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/LLDBWrapPython.cpp
     )