Optional Impala Toolchain

This patch allows to optionally enable the new Impala binary
toolchain. For now there are now major version differences in the
toolchain dependencies and what is currently kept in thirdparty.

To enable the toolchain, export the variable IMPALA_TOOLCHAIN to the
folder where the binaries are available.

In addition this patch moves gutil from the thirdparty directory into
the source tree of be/src to allow easy propagation of compiler and
linker flags. Furthermore, the thrift-cpp target was added as a
dependency to all targets that require the generated thrift sources to
be available before the build is started.

What is the new toolchain: The goal of the toolchain is to homogenize
the build environment and to make sure that Impala is build nearly
identical on every platform. To achieve this, we limit the flexibility
of using the systems host libraries and rather rely on a set of custom
produced binaries including the necessary compiler.

Change-Id: If2dac920520e4a18be2a9a75b3184a5bd97a065b
Reviewed-on: http://gerrit.cloudera.org:8080/427
Reviewed-by: Adar Dembo <adar@cloudera.com>
Tested-by: Internal Jenkins
Reviewed-by: Martin Grund <mgrund@cloudera.com>

cmake_modules/FindRapidJson.cmake

@@ -1,25 +1,20 @@
 # - Find rapidjson headers and lib.
+# RAPIDJSON_ROOT hints the location
 # This module defines RAPIDJSON_INCLUDE_DIR, the directory containing headers
 
 set(RAPIDJSON_SEARCH_HEADER_PATHS
+  ${RAPIDJSON_ROOT}/include
   ${CMAKE_SOURCE_DIR}/thirdparty/rapidjson/include/
 )
 
 find_path(RAPIDJSON_INCLUDE_DIR rapidjson/rapidjson.h HINTS
   ${RAPIDJSON_SEARCH_HEADER_PATHS})
 
-if (RAPIDJSON_INCLUDE_DIR)
-  set(RAPIDJSON_FOUND TRUE)
-else ()
+if (NOT RAPIDJSON_INCLUDE_DIR)
+  message(FATA_ERROR "RapidJson headers NOT found.")
   set(RAPIDJSON_FOUND FALSE)
-endif ()
-
-if (RAPIDJSON_FOUND)
-  if (NOT RAPIDJSON_FIND_QUIETLY)
-    message(STATUS "RapidJson headers found in: ${RAPIDJSON_INCLUDE_DIR}")
-  endif ()
-else ()
-  message(STATUS "RapidJson headers NOT found.")
+else()
+  set(RAPIDJSON_FOUND TRUE)
 endif ()
 
 mark_as_advanced(