[SYCL][CMake] Build RelWithDebInfo sycl runtimes with frame pointers

[tcreech-intel]

Enable frame pointers on sycl runtimes when the build configuration is
Debug or RelWithDebInfo. (Though setting this will typically be a no-op
for Debug builds.)

Frame pointers improve the effectiveness of profilers, tracers, and
other introspection tools.

[tcreech-intel]

I was double-checking compile_commands.json and realized some compilations I was expecting to have the flag did not.
This is fixed in bb5484c, which also sets the flags for the object library as we do with (for example) code coverage options. The general idea is the same.

[bashbaug]

LGTM! I didn't do a thorough check, but in my spot checks had -fno-omit-frame-pointer in the places where I expected to see it.