adt-installer: add warning if MACHINE is not set in adt-installer.conf

adt-installer: add warning if MACHINE is not set in adt-installer.conf

Since the MACHINE can now be specified in adt-installer.conf, in order to
install the proper toolchain and environment script for the given
machine, add a sanity checking at the beginning to make sure MACHINE is
set for the wanted architecture.

Also:
 * uncomment the x86 target variables, in adt-installer.conf, in order
   to have qemux86 MACHINE set, by default, and also the sysroot
   installed (since it doesn't make much sense to install the toolchain
   without a target sysroot);
 * remove 'sudo' when creating relocate_sdk_tmp.py because the file is
   created in adt-installer directory;

[YOCTO #5259]

(From OE-Core rev: 0623a0e1bd7cf0c405a0469e9f16779971c0c3b5)

Signed-off-by: Laurentiu Palcu <laurentiu.palcu@intel.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>