Backed out changeset 4356b6a222c7: forcing DEBUG_PREBUILT output.

It appears that our trouble was due to a cygwin-style path in the AUTOBUILD
environment variable, and that changeset 0e0bd8b546ad fixed it.

indra/cmake/Prebuilt.cmake

@@ -16,13 +16,6 @@ if ("${CMAKE_SOURCE_DIR}/../autobuild.xml" IS_NEWER_THAN "${PREBUILD_TRACKING_DI
   file(WRITE ${PREBUILD_TRACKING_DIR}/sentinel_installed "0")
 endif ("${CMAKE_SOURCE_DIR}/../autobuild.xml" IS_NEWER_THAN "${PREBUILD_TRACKING_DIR}/sentinel_installed")
 
-# <HACK> to debug use_prebuilt_binary failures on TC host
-IF (NOT DEFINED DEBUG_PREBUILT)
-  set(DEBUG_PREBUILT ON)
-  message(STATUS "AUTOBUILD = '$ENV{AUTOBUILD}'")
-ENDIF (NOT DEFINED DEBUG_PREBUILT)
-# </HACK>
-
 # The use_prebuilt_binary macro handles automated installation of package
 # dependencies using autobuild.  The goal is that 'autobuild install' should
 # only be run when we know we need to install a new package.  This should be