ML-KEM: check CPU features before calling kyber_rvv_selector

On RISC-V platforms without V, kyber_rvv_selector is called first in
__attribute__((constructor)) before the normal dynamic dispatch code in
kyber_kem_api_riscv.c, causing SIGILL. Add a condition so that
lc_cpu_feature_available() is always first checked.

Signed-off-by: Eric Long <i@hack3r.moe>
Signed-off-by: Stephan Mueller <smueller@chronox.de>

Author: hack3ric

ml-kem/src/riscv64/kyber_rvv_vlen_selector.c

@@ -17,6 +17,7 @@
  * DAMAGE.
  */
 
+#include "cpufeatures.h"
 #include "ext_headers_riscv.h"
 #include "initialization.h"
 #include "kyber_rvv_vlen_selector.h"
@@ -28,9 +29,11 @@ static int lc_riscv_rvv_vlen = 0;
 
 LC_CONSTRUCTOR(kyber_riscv_rvv_selector)
 {
-	LC_VECTOR_ENABLE;
-	lc_riscv_rvv_vlen = kyber_rvv_selector();
-	LC_VECTOR_DISABLE;
+	if (lc_cpu_feature_available() & LC_CPU_FEATURE_RISCV_ASM_RVV) {
+		LC_VECTOR_ENABLE;
+		lc_riscv_rvv_vlen = kyber_rvv_selector();
+		LC_VECTOR_DISABLE;
+	}
 }
 
 int lc_riscv_rvv_is_vlen128(void)