selftest: unwrap system() exit status on Linux (RunBitflashChild)

The Linux branch of the child-process helper returned system()s raw wait
status instead of the exit code, so an exit code of 2 read back as 512.
Every assertion that checks a specific code (== 2), like the locked
recovery-audit test, failed only on Linux while the node itself was
correct. Windows was unaffected (_spawnv returns the code directly).

Unwrap with WIFEXITED/WEXITSTATUS so both platforms return the same value.
Test harness only; no change to node behavior.

1 files changed, 10 insertions, 1 deletions

diff --git a/src/selftest.cpp b/src/selftest.cpp
index a9c73fe..dc9936e 100644
--- a/src/selftest.cpp
+++ b/src/selftest.cpp
@@ -10,6 +10,9 @@
 #include "bip32.h"
 #include "proxy.h"
 #include "selftest.h"
+#ifndef _WIN32
+#include <sys/wait.h>   // WIFEXITED/WEXITSTATUS for the child-process helper
+#endif
 #include "sockcount.h"
 #include "tor.h"
 #include "walletcmd.h"
@@ -2110,7 +2113,13 @@ static int RunBitflashChild(const string& strExe,
         strCmd += " > " + QuoteCommandArg(*pOutputFile) + " 2>&1";
     else
         strCmd += " > /dev/null 2>&1";
-    return system(strCmd.c_str());
+    // system() returns a wait status, not the exit code; unwrap it so callers
+    // see the same value the Windows _spawnv path returns (e.g. exit code 2 is
+    // 2, not 512). Without this every "== 2" assertion fails only on Linux.
+    int nSysRet = system(strCmd.c_str());
+    if (nSysRet != -1 && WIFEXITED(nSysRet))
+        return WEXITSTATUS(nSysRet);
+    return nSysRet;
 #endif
 }