Run the C preprocessor across the instruction definition files and macro
definition file to expand macros and prepare the semantics_generated.pyinc
file.  The resulting file contains one entry with the semantics for each
instruction and one line with the instruction attributes associated with
each macro.

Signed-off-by: Taylor Simpson <tsimpson@quicinc.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <1612763186-18161-20-git-send-email-tsimpson@quicinc.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>