The monotonic uptime fix (#34328) used a function-local static for `g_startup_time`, which was initialized on first `GetUptime()` call instead of app startup time.
This caused the first `uptime()` call to always return 0.
Move `g_startup_time` to namespace scope so it initializes at program start, ensuring the first call returns actual elapsed time. Note that we don't need to make it `static` anymore because it is just used in this single translation unit.
Test was updated to simulate some work before the first call.
Co-authored-by: Carlo Antinarella <carloantinarella@users.noreply.github.com>
Compute `uptime` from `SteadyClock` so it is unaffected by system time changes after startup.
Derive GUI startup time by subtracting the monotonic uptime from the wall clock time.
Add a functional test covering a large `setmocktime` jump.
Co-authored-by: MarcoFalke <*~=`'#}+{/-|&$^_@721217.xyz>
The previous diff touched most files in ./test/, so bump the headers to
avoid having to touch them again for a bump later.
-BEGIN VERIFY SCRIPT-
./contrib/devtools/copyright_header.py update ./test/
-END VERIFY SCRIPT-
