Escape file write expansion, and build up lists.

Escaped the @var@ in the file writes - this was being expanded at file
write and so not causing a reconfigure at the right time. I also took
care of build up lists of lists in the variables, especially important
for things like MPI_EXTRA_LIBRARY. Added some error checking, and use
the tmp_dir for initial cache file.

Modules/ExternalProject.cmake

@@ -554,23 +554,36 @@ function(_ep_write_initial_cache script_filename args)
   # Write out values into an initial cache, that will be passed to CMake with -C
   set(script_initial_cache "")
   set(regex "^([^:]+):([^=]+)=(.*)$")
+  set(setArg "")
   foreach(line ${args})
-    string(REGEX REPLACE "^-D" "" line ${line})
-    if("${line}" MATCHES "${regex}")
-      string(REGEX MATCH "${regex}" match "${line}")
-      set(name "${CMAKE_MATCH_1}")
-      set(type "${CMAKE_MATCH_2}")
-      set(value "${CMAKE_MATCH_3}")
-      set(setArg "set(${name} \"${value}\" CACHE ${type} \"Initial cache\" FORCE)")
-      set(script_initial_cache "${script_initial_cache}\n${setArg}")
+    if("${line}" MATCHES "^-D")
+      if(setArg)
+        # This is required to build up lists in variables, or complete an entry
+        set(setArg "${setArg}${accumulator}\" CACHE ${type} \"Initial cache\" FORCE)")
+        set(script_initial_cache "${script_initial_cache}\n${setArg}")
+        set(accumulator "")
+        set(setArg "")
+      endif()
+      string(REGEX REPLACE "^-D" "" line ${line})
+      if("${line}" MATCHES "${regex}")
+        string(REGEX MATCH "${regex}" match "${line}")
+        set(name "${CMAKE_MATCH_1}")
+        set(type "${CMAKE_MATCH_2}")
+        set(value "${CMAKE_MATCH_3}")
+        set(setArg "set(${name} \"${value}")
+      else()
+        message(WARNING "Line '${line}' does not match regex. Ignoring.")
+      endif()
+    else()
+      # Assume this is a list to append to the last var
+      set(accumulator "${accumulator};${line}")
     endif()
   endforeach()
   # Write out the initial cache file to the location specified.
   if(NOT EXISTS "${script_filename}.in")
-    file(WRITE "${script_filename}.in" "@script_initial_cache@\n")
+    file(WRITE "${script_filename}.in" "\@script_initial_cache\@\n")
   endif()
   configure_file("${script_filename}.in" "${script_filename}")
-
 endfunction(_ep_write_initial_cache)
 
 
@@ -1251,7 +1264,7 @@ function(_ep_add_configure_command name)
     # If there are any CMAKE_CACHE_ARGS, write an initial cache and use it
     get_property(cmake_cache_args TARGET ${name} PROPERTY _EP_CMAKE_CACHE_ARGS)
     if(cmake_cache_args)
-      set(_ep_cache_args_script "${CMAKE_CURRENT_BINARY_DIR}/${name}-cache.cmake")
+      set(_ep_cache_args_script "${tmp_dir}/${name}-cache.cmake")
       _ep_write_initial_cache("${_ep_cache_args_script}" "${cmake_cache_args}")
       list(APPEND cmd "-C${_ep_cache_args_script}")
     endif()
@@ -1274,7 +1287,7 @@ function(_ep_add_configure_command name)
   # Fixes issue http://public.kitware.com/Bug/view.php?id=10258
   #
   if(NOT EXISTS ${tmp_dir}/${name}-cfgcmd.txt.in)
-    file(WRITE ${tmp_dir}/${name}-cfgcmd.txt.in "cmd='@cmd@'\n")
+    file(WRITE ${tmp_dir}/${name}-cfgcmd.txt.in "cmd='\@cmd\@'\n")
   endif()
   configure_file(${tmp_dir}/${name}-cfgcmd.txt.in ${tmp_dir}/${name}-cfgcmd.txt)
   list(APPEND file_deps ${tmp_dir}/${name}-cfgcmd.txt)