Bug #18593044 COMPILE FLAGS NOT PASSED TO DTRACE, BREAKS CROSS BUILD

RHEL7/Oracle Linux 7 comes in 64 bits variants only, however at
least libraries are required in 32 bits versions too.  Going
forward there might be need for 32 bits clients.
 
RHEL/OL7 supports cross build of 32 bits binaries on 64 bits platform.
 
This works just fine for MySQL server also, however when dtrace
is enabled build fails.
 
Due to the fact that dtrace on Linux is running gcc and reading
CFLAGS from environment only.
(Just reading last part of /usr/bin/dtrace to verify this).
 
When cross building a 32 bits server package, flags includes
-m32, however this is not passed to dtrace, which builds a 64
bits probes_mysql.o, which cause link error by mixing 32 of 64
bits object files.

Author: Tor Didriksen

cmake/dtrace.cmake

@@ -1,4 +1,4 @@
-# Copyright (c) 2009, 2013, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 2009, 2014, Oracle and/or its affiliates. All rights reserved.
 # 
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -110,12 +110,16 @@ FUNCTION(DTRACE_INSTRUMENT target)
         WORKING_DIRECTORY ${objdir}
       )
     ELSEIF(CMAKE_SYSTEM_NAME MATCHES "Linux")
+      # dtrace on Linux runs gcc and uses flags from environment
+      SET(CFLAGS_SAVED $ENV{CFLAGS})
+      SET(ENV{CFLAGS} ${CMAKE_C_FLAGS})
       SET(outfile "${CMAKE_BINARY_DIR}/probes_mysql.o")
       # Systemtap object
       EXECUTE_PROCESS(
         COMMAND ${DTRACE} -G -s ${CMAKE_SOURCE_DIR}/include/probes_mysql.d.base
         -o ${outfile}
         )
+      SET(ENV{CFLAGS} ${CFLAGS_SAVED})
     ENDIF()
 
     # Do not try to extend the library if we have not built the .o file