Add memory clobber to WITH_BACKUP_RAM_RW asm

[dogruis]

Without a memory clobber, gcc -O2 may reorder reads/writes of backup-RAM globals across the unlock/lock pair in WITH_BACKUP_RAM_RW, defeating the protection. Adding ::: "memory" to both asm volatile blocks makes them proper compiler barriers without changing emitted code for the asm itself.

Code example:

WITH_BACKUP_RAM_RW({
    high_score = new_score;       // BRAM write
    save_count = save_count + 1;  // BRAM write
});
some_other_global = 0;            // non-BRAM

Without "memory", gcc might rearrange to:

unlock_asm();
some_other_global = 0;            // moved INTO the protected section (harmless but pointless)
high_score = new_score;
lock_asm();
save_count = save_count + 1;      // moved OUT to AFTER the lock — bug!

The save_count write happens while BRAM is re-locked → hardware rejects the write → save data corrupted on the next save cycle.

[dciabrin]

LGTM
Thank you

[dogruis]

Oh... That's great I have became a contributor!!!!! This made my day 😄

[dciabrin]

Oops, that commit broke the build on all arch :)
I should enable the CI runs for pull requests. I'll fix the commit later today

[dciabrin]

Fixed in 28b5276