i#1620 WIX integration: Started development on WIX

This commit starts the process of using WIX as our installer
with windows. The editing of registry and overwiting of previous
installations of Dr. Memory needs to be verified.

Review-URL: https://codereview.appspot.com/175380043

CMakeLists.txt

@@ -2004,8 +2004,20 @@ else (UNIX)
       endif ()
     endif (strings)
   else (NSIS)
-    message(STATUS "NSIS not found: will not build installer")
-    set(CPACK_GENERATOR "ZIP")
+    # XXX i#1620: To switch entirely from NSIS to WIX
+    # will need to generate GUID's to install over previous NSIS installs and
+    # to make sure registry values are written to that were originally done
+    # with tools/vs_external_tool.c
+    message(STATUS "NSIS not found: will try building with WIX")
+    find_program(WIX candle HINT "$ENV{PROGRAMFILES}/bin" DOC "WIX for creating installer")
+    if (WIX)
+      # Make sure to specify BUILDING_PACKAGE. See i#1099 about absolute path.
+      message(STATUS "WIX found. Using WIX to install")
+      set(CPACK_GENERATOR "ZIP;WIX")
+    else (WIX)
+      message(STATUS "WIX compiler candle.exe not found. Please add it to path or install the WIX tooset. Installing as a Zip")
+      set(CPACK_GENERATOR "ZIP")
+    endif (WIX)
   endif (NSIS)
   set(CPACK_SOURCE_GENERATOR "ZIP")
   set(CPACK_SYSTEM_NAME "Windows")