sim: m32r: migrate ftime() to clock_gettime()

sim: m32r: migrate ftime() to clock_gettime()

The ftime() function has been deprecated since POSIX-1-2004, and
removed in POSIX.1-2008.  It's also been deprecated/removed in glibc
since 2.33.  POSIX has always said the function is not portable, and
its return value, timezone, and dstflag fields are unspecified.  Even
if Linux/glibc & m32r had defined behavior, those aren't the host for
the sim runtime.

So let's stop using the function and switch to clock_gettime.  gnulib
already has detection support for it, and it's been around since at
least POSIX-1-2004.