[client] Disable pidfd check on Android 11 and below (#4127)

Disable pidfd check on Android 11 and below

On Android 11 (SDK <= 30) and earlier, pidfd-related system calls
are blocked by seccomp policies, causing SIGSYS crashes.

This change overrides `checkPidfdOnce` to return an error on
affected versions, preventing the use of unsupported pidfd features.

client/android/exec.go

@@ -0,0 +1,26 @@
+//go:build android
+
+package android
+
+import (
+	"fmt"
+	_ "unsafe"
+)
+
+// https://github.com/golang/go/pull/69543/commits/aad6b3b32c81795f86bc4a9e81aad94899daf520
+// In Android version 11 and earlier, pidfd-related system calls
+// are not allowed by the seccomp policy, which causes crashes due
+// to SIGSYS signals.
+
+//go:linkname checkPidfdOnce os.checkPidfdOnce
+var checkPidfdOnce func() error
+
+func execWorkaround(androidSDKVersion int) {
+	if androidSDKVersion > 30 { // above Android 11
+		return
+	}
+
+	checkPidfdOnce = func() error {
+		return fmt.Errorf("unsupported Android version")
+	}
+}