diff --git a/indra/CMakeLists.txt b/indra/CMakeLists.txt
index 310e6cbdd42a7b16c70b5fe227d95b674e0d811a..d1042d6e8693ff4692a105d24885081e6a4a233d 100644
--- a/indra/CMakeLists.txt
+++ b/indra/CMakeLists.txt
@@ -35,8 +35,10 @@ endif (NOT CMAKE_BUILD_TYPE)
 
 # For the library installation process;
 # see cmake/Prebuild.cmake for the counterpart code.
-file(MAKE_DIRECTORY ${CMAKE_BINARY_DIR}/temp)
-file(WRITE ${CMAKE_BINARY_DIR}/temp/sentinel_installed "0")
+if ("${CMAKE_SOURCE_DIR}/../autobuild.xml" IS_NEWER_THAN "${CMAKE_BINARY_DIR}/temp/sentinel_installed")
+  file(MAKE_DIRECTORY ${CMAKE_BINARY_DIR}/temp)
+  file(WRITE ${CMAKE_BINARY_DIR}/temp/sentinel_installed "0")
+endif ("${CMAKE_SOURCE_DIR}/../autobuild.xml" IS_NEWER_THAN "${CMAKE_BINARY_DIR}/temp/sentinel_installed")
 add_subdirectory(cmake)
 
 add_subdirectory(${LIBS_OPEN_PREFIX}llaudio)
diff --git a/indra/cmake/Prebuilt.cmake b/indra/cmake/Prebuilt.cmake
index 1b60d176f11d141269c664a50b71a189a2e1448a..dbb4dfc46c7f034c792224ac52a33269be1e8028 100644
--- a/indra/cmake/Prebuilt.cmake
+++ b/indra/cmake/Prebuilt.cmake
@@ -1,35 +1,49 @@
 # -*- cmake -*-
 
 include(FindAutobuild)
+if(INSTALL_PROPRIETARY)
+  include(FindSCP)
+endif(INSTALL_PROPRIETARY)
 
+# 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
+# the case in a clean checkout, or if autobuild.xml has been updated since the
+# last run (encapsulated by the file ${CMAKE_BINARY_DIR}/temp/sentinel_installed),
+# or if a previous attempt to install the package has failed (the exit status
+# of previous attempts is serialized in the file
+# ${CMAKE_BINARY_DIR}/temp/${_binary}_installed)
 macro (use_prebuilt_binary _binary)
   if (NOT DEFINED STANDALONE_${_binary})
     set(STANDALONE_${_binary} ${STANDALONE})
   endif (NOT DEFINED STANDALONE_${_binary})
 
   if (NOT STANDALONE_${_binary})
-    if(${CMAKE_BINARY_DIR}/temp/sentinel_installed IS_NEWER_THAN ${CMAKE_BINARY_DIR}/temp/${_binary}_installed)
-      if(INSTALL_PROPRIETARY)
-        include(FindSCP)
-      endif(INSTALL_PROPRIETARY)
-	  if(DEBUG_PREBUILT)
-		message("cd ${CMAKE_SOURCE_DIR} && ${AUTOBUILD_EXECUTABLE} install
-		--install-dir=${AUTOBUILD_INSTALL_DIR}
-		--skip-license-check
-		${_binary} ")
-	  endif(DEBUG_PREBUILT)
-	  execute_process(COMMAND "${AUTOBUILD_EXECUTABLE}"
-		install
-		--install-dir=${AUTOBUILD_INSTALL_DIR}
-		--skip-license-check
-		${_binary}
-		WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}"
-		RESULT_VARIABLE ${_binary}_installed
-		)
+    if("${${_binary}_installed}" STREQUAL "" AND EXISTS "${CMAKE_BINARY_DIR}/temp/${_binary}_installed")
+      file(READ ${CMAKE_BINARY_DIR}/temp/${_binary}_installed "${_binary}_installed")
+      if(DEBUG_PREBUILT)
+        message(STATUS "${_binary}_installed: \"${${_binary}_installed}\"")
+      endif(DEBUG_PREBUILT)
+    endif("${${_binary}_installed}" STREQUAL "" AND EXISTS "${CMAKE_BINARY_DIR}/temp/${_binary}_installed")
+
+    if(${CMAKE_BINARY_DIR}/temp/sentinel_installed IS_NEWER_THAN ${CMAKE_BINARY_DIR}/temp/${_binary}_installed OR NOT ${${_binary}_installed} EQUAL 0)
+      if(DEBUG_PREBUILT)
+        message("cd ${CMAKE_SOURCE_DIR} && ${AUTOBUILD_EXECUTABLE} install
+        --install-dir=${AUTOBUILD_INSTALL_DIR}
+        --skip-license-check
+        ${_binary} ")
+      endif(DEBUG_PREBUILT)
+      execute_process(COMMAND "${AUTOBUILD_EXECUTABLE}"
+        install
+        --install-dir=${AUTOBUILD_INSTALL_DIR}
+        --skip-license-check
+        ${_binary}
+        WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}"
+        RESULT_VARIABLE ${_binary}_installed
+        )
       file(WRITE ${CMAKE_BINARY_DIR}/temp/${_binary}_installed "${${_binary}_installed}")
-    else(${CMAKE_BINARY_DIR}/temp/sentinel_installed IS_NEWER_THAN ${CMAKE_BINARY_DIR}/temp/${_binary}_installed)
-      set(${_binary}_installed 0)
-    endif(${CMAKE_BINARY_DIR}/temp/sentinel_installed IS_NEWER_THAN ${CMAKE_BINARY_DIR}/temp/${_binary}_installed)
+    endif(${CMAKE_BINARY_DIR}/temp/sentinel_installed IS_NEWER_THAN ${CMAKE_BINARY_DIR}/temp/${_binary}_installed OR NOT ${${_binary}_installed} EQUAL 0)
+
     if(NOT ${_binary}_installed EQUAL 0)
       message(FATAL_ERROR
               "Failed to download or unpack prebuilt '${_binary}'."