tools/libacpi: fix sed usage

tools/libacpi: fix sed usage

Current usage of sed in the libacpi Makefile make uses of non-POSIX options,
that are not available on all the OSes supported by the Xen tools.

The '-i' option has slightly different semantics between GNU and BSD sed
implementations, while on the GNU version the suffix is optional, on the BSD
one it is not. Also BSD sed seems to have problems parsing the script
itself, reporting "extra characters at the end of d command".

Fix those issues by using a temporary intermediate file, and replace the
script with a simpler version that achieves the same purpose (removing the
initial license header comment).

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Release-acked-by: Wei Liu <wei.liu2@citrix.com>