4.9 backport request: perf tools: Fix build with ARCH=x86_64

[Tuomas Tynkkynen <tuomas@tuxera.com>]

Hi Greg,

Please apply the following commit from 4.10 to 4.9.y to fix perf build
under certain conditions:

commit 7a759cd8e8272ee18922838ee711219c7c796a31                                        
Author: Jiada Wang <jiada_wang@mentor.com>
Date:   Sun Apr 9 20:02:37 2017 -0700

    perf tools: Fix build with ARCH=x86_64
    
    With commit: 0a943cb10ce78 (tools build: Add HOSTARCH Makefile variable)
    when building for ARCH=x86_64, ARCH=x86_64 is passed to perf instead of
    ARCH=x86, so the perf build process searchs header files from
    tools/arch/x86_64/include, which doesn't exist.
    
    The following build failure is seen:
    
      In file included from util/event.c:2:0:
        tools/include/uapi/linux/mman.h:4:27: fatal error: uapi/asm/mman.h: No such file or directory
        compilation terminated.
    
    Fix this issue by using SRCARCH instead of ARCH in perf, just like the
    main kernel Makefile and tools/objtool's.
    
    Signed-off-by: Jiada Wang <jiada_wang@mentor.com>
    Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
    Acked-by: Jiri Olsa <jolsa@kernel.org>
    Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
    Cc: Andi Kleen <ak@linux.intel.com>
    Cc: Eugeniu Rosca <erosca@de.adit-jv.com>
    Cc: Jan Stancek <jstancek@redhat.com>
    Cc: Masami Hiramatsu <mhiramat@kernel.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
    Cc: Rui Teng <rui.teng@linux.vnet.ibm.com>
    Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
    Cc: Wang Nan <wangnan0@huawei.com>
    Fixes: 0a943cb10ce7 ("tools build: Add HOSTARCH Makefile variable")
    Link: http://lkml.kernel.org/r/1491793357-14977-2-git-send-email-jiada_wang@mentor.com
    Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Thanks.