This change reduces the space occupied by struct pthread_attr
which is the internal type used for pthread_attr_t.
We cap the stack size at 16 bits (so up to 65536 bytes) and
since a stack size of 0 is invalid, we can encode the stack
size by simply subtracting 1 or adding 1 when setting or
getting.
The schedpolicy is capped at 2 bits and initialized,
cancellable, and detached are given 1 bit.
Signed-off-by: Christopher Friedt <cfriedt@meta.com>
eb7e4bed98