Ignore fuchsia tests implicitly relying on a signal upon abort

Both test-panic-abort-nocapture.rs and test-panic-abort.rs assert the
stderr output of the test. On Fuchsia, if a test fails an assertion,
this output will contain a line noting the process returned the code
-1028 (ZX_TASK_RETCODE_EXCEPTION_KILL). But the asserted stderr output
lacks this note. Presumably this is because other platforms implement
-Cpanic=abort by killing the process instead of returned a status
code.

tests/ui/test-attrs/test-panic-abort-nocapture.rs

@@ -10,6 +10,7 @@
 //@ ignore-wasm no panic or subprocess support
 //@ ignore-emscripten no panic or subprocess support
 //@ ignore-sgx no subprocess support
+//@ ignore-fuchsia code returned as ZX_TASK_RETCODE_EXCEPTION_KILL, FIXME (#127539)
 
 #![cfg(test)]
 

tests/ui/test-attrs/test-panic-abort-nocapture.run.stderr

@@ -1,9 +1,9 @@
-thread 'main' panicked at $DIR/test-panic-abort-nocapture.rs:34:5:
+thread 'main' panicked at $DIR/test-panic-abort-nocapture.rs:35:5:
 assertion `left == right` failed
   left: 2
  right: 4
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
-thread 'main' panicked at $DIR/test-panic-abort-nocapture.rs:28:5:
+thread 'main' panicked at $DIR/test-panic-abort-nocapture.rs:29:5:
 assertion `left == right` failed
   left: 2
  right: 4

tests/ui/test-attrs/test-panic-abort.rs

@@ -10,6 +10,7 @@
 //@ ignore-wasm no panic or subprocess support
 //@ ignore-emscripten no panic or subprocess support
 //@ ignore-sgx no subprocess support
+//@ ignore-fuchsia code returned as ZX_TASK_RETCODE_EXCEPTION_KILL, FIXME (#127539)
 
 #![cfg(test)]
 #![feature(test)]

tests/ui/test-attrs/test-panic-abort.run.stdout

@@ -17,7 +17,7 @@ hello, world
 testing123
 ---- it_fails stderr ----
 testing321
-thread 'main' panicked at $DIR/test-panic-abort.rs:39:5:
+thread 'main' panicked at $DIR/test-panic-abort.rs:40:5:
 assertion `left == right` failed
   left: 2
  right: 5