AP_HAL: test concurrent storage writes on SITL and Linux

Exercise same-line updates and concurrent dirtying of another line for
one million rounds, yielding so single-CPU runners make progress. On Linux
hosts, also stall backend IO to verify buffer access and persistence of
concurrent writes, and inject a SITL write failure to check dirty-line retry.

libraries/AP_HAL/examples/StorageRace/wscript

@@ -0,0 +1,12 @@
+#!/usr/bin/env python3
+
+import sys
+
+
+def build(bld):
+    if bld.env.BOARD not in ('sitl', 'linux'):
+        return
+    linkflags = []
+    if sys.platform.startswith('linux'):
+        linkflags = ['-Wl,--wrap=pwrite', '-Wl,--wrap=write']
+    bld.ap_example(use='ap', linkflags=linkflags)