ci+fix: link the exported UCRT time symbols; gdb over copier_test too

- localtime_s/gmtime_s are MinGW header inlines, not symbols — link
  _localtime64_s/_gmtime64_s
- copier_test also segfaults only on the Linux runner; add it to the
  on-failure gdb backtrace

.github/workflows/ci.yml

@@ -212,7 +212,7 @@ jobs:
         if: failure()
         run: |
           sudo apt-get install -y gdb
-          for name in node_e2e_test suites_test; do
+          for name in node_e2e_test suites_test copier_test; do
             BIN=$(ls -t target/debug/deps/$name-* | grep -v '\.d$' | head -1)
             [ -n "$BIN" ] || continue
             xvfb-run -a gdb -batch -ex run -ex bt -- "$BIN" --nocapture || true

crates/oaknode/src/nodes/timeformat.rs

@@ -76,8 +76,10 @@ extern "C" {
 }
 #[cfg(target_os = "windows")]
 extern "C" {
-	fn localtime_s(result: *mut Tm, timep: *const i64) -> i32;
-	fn gmtime_s(result: *mut Tm, timep: *const i64) -> i32;
+	// UCRT exports the 64-bit-time variants; `localtime_s`/`gmtime_s` are
+	// header inlines on MinGW, not linkable symbols.
+	fn _localtime64_s(result: *mut Tm, timep: *const i64) -> i32;
+	fn _gmtime64_s(result: *mut Tm, timep: *const i64) -> i32;
 }
 
 /// Expand Qt date/time format tokens (`QDateTime::toString` syntax):
@@ -306,9 +308,9 @@ impl NodeBehavior for TimeFormatNode {
 		unsafe {
 			let secs64 = secs as i64;
 			if to_bool(&local_val) {
-				localtime_s(&mut tm, &secs64);
+				_localtime64_s(&mut tm, &secs64);
 			} else {
-				gmtime_s(&mut tm, &secs64);
+				_gmtime64_s(&mut tm, &secs64);
 			}
 		}