signing.bbclass: drop dead OpenSSL engine handling

signing_prepare() signs via the pkcs11 provider only: it writes a provider
openssl.cnf and uses OSSL_STORE for native provider access. Nothing invokes
the OpenSSL ENGINE API (no -engine), so the OPENSSL_ENGINES export and the
engines-3 directory check are dead code. The check even hard-fails
(return 1) when engines-3 is absent, which OpenSSL 4.0 no longer ships
(ENGINE API removed) - breaking signing outright although the provider path
is fine. Remove the engine export and the check.

Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Johannes Schneider <johannes.schneider@leica-geosystems.com>
Signed-off-by: Khem Raj <khem.raj@oss.qualcomm.com>

meta-oe/classes/signing.bbclass

@@ -337,7 +337,6 @@ signing_import_install() {
 
 signing_prepare() {
     export OPENSSL_MODULES="${STAGING_LIBDIR_NATIVE}/ossl-modules"
-    export OPENSSL_ENGINES="${STAGING_LIBDIR_NATIVE}/engines-3"
     export OPENSSL_CONF="${STAGING_LIBDIR_NATIVE}/openssl-provider-signing.cnf"
     export SSL_CERT_DIR="${STAGING_LIBDIR_NATIVE}/ssl-3/certs"
     export SSL_CERT_FILE="${STAGING_LIBDIR_NATIVE}/ssl-3/cert.pem"
@@ -348,12 +347,6 @@ signing_prepare() {
         echo "Missing OpenSSL module directory at '${OPENSSL_MODULES}'"
         return 1
     fi
-    if [ -d ${OPENSSL_ENGINES} ]; then
-        echo "Using '${OPENSSL_ENGINES}' for OpenSSL run-time PKCS#11 modules"
-    else
-        echo "Missing OpenSSL PKCS11 engine directory at '${OPENSSL_ENGINES}'"
-        return 1
-    fi
 
     export SOFTHSM2_CONF="${WORKDIR}/softhsm2.conf"
     export SOFTHSM2_DIR="${STAGING_DIR_NATIVE}/var/lib/softhsm/tokens"