This function always returns the same value for a given thread.
Add the const attribute to it so the compiler won't call it over and
over needlessly each time _current is referenced, making for far more
efficient code.
The __attribute_const__ symbol is used to mimic the Linux equivalent.
We want to make it clear that this is distinct from the const keyword.
Fix the test_x86_cpu_scrubs_regs where the compiler wasn't told that a
bunch of registers are being clobbered as highlighted by this change.
Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
0dc7b9ee46