crosstap: handle hyphenated x86_64 target arch

crosstap: handle hyphenated x86_64 target arch

systemtap_target_arch() should also translate x86-64 (hyphenated) into
x86_64 for the -a param.  Failing to do that causes systemtap to see
an architecture mismatch and create a cloned session with a bogusly
synthesized build directory path, and fails to compile the probe.

 Fixes [YOCTO #3756]

(From OE-Core rev: 98cae0544884cb5700d42409ec4a9584a17dc9a4)

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