where are newlib configuration options

We use ARM's GCC for Cortex-M (actually, as redistributed by NXP etc.).
I must rebuild newlib (to get a debug version of the library, as ARM seems not to supply that).
Where can I find the set of configuration command options used to build newlib for ARM's GCC toolchain distribution?
There should be several for the combinations of nano, nohost options.
Thanks in advance,
Best Regards, Dave

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