asm-offsets: encode magic asm-offset runes as strings.

asm-offsets: encode magic asm-offset runes as strings.

Newer versions of clang attempt to parse inline assembler even when
not asked to assemble it.  Wrap our not-for-assembly runes as strings
of the form ``.ascii "==>MAGIC RUNES<=="'' so clang doesn't choke on
them.

While we're at it, assemble more of the final output line in the C
file, to make the sed expression shorter.

Reported-by: Julien Grall <julien.grall@linaro.org>
Suggested-by: Jan Beulich <JBeulich@suse.com>
Signed-off-by: Tim Deegan <tim@xen.org>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>