linux-yocto/3.8: Makefile: add -grecord-gcc-switches if using -mfentry

linux-yocto/3.8: Makefile: add -grecord-gcc-switches if using -mfentry

    Commit a2546fae [ftrace: Add -mfentry to Makefile on function tracer]
    adds support for using -mfentry when possible, whenever the ftrace
    CONFIG_FUNCTION_TRACER option is enabled.

    This unfortunately causes bogus dwarf debuginfo to be generated:

      gcc Bug 54793 - the location of a formal_parameter is not started from a
                      function entry with -mfentry

      http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54793

    This can be fixed by applying the gcc patch above, which will be
    present in gcc-4.8, but in the meantime, the problem is currently
    being worked around in different ways by various tools.  One of those
    tools that we support in Yocto, Systemtap, requires the DW_AT_producer
    string contain -mfentry, which means that it's assuming
    record-gcc-switches is also used:

      SystemTap Bug 15123 - workaround for bad debuginfo for -mfentry
      http://sourceware.org/bugzilla/show_bug.cgi?id=15123

    The lack of -grecord-gcc-switches and therefore a missing -mfentry
    string in Yocto leads to the following Yocto bug:

      Bug 4099 - Crosstap script check fails
      https://bugzilla.yoctoproject.org/show_bug.cgi?id=4099

    Which is what this patch intends to fix.

    It only affects architectures that HAVE_FENTRY when
    CONFIG_FUNCTION_TRACER is turned on and in any case is just adding to
    the debuginfo, so there doesn't seem to be much risk to adding it.

(From OE-Core rev: c04f611aa4bf77867fe78a005d09434226feb62c)

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>