cross-platform compilation error patch (lilke win only patch https://github.com/microsoft/vcpkg/blob/master/ports/libtommath/msvc-dce.patch)

Author: Khalyutin

extern/libtommath/bn_s_mp_rand_platform.c

@@ -137,11 +137,21 @@ mp_err s_read_ltm_rng(void *p, size_t n);
 mp_err s_mp_rand_platform(void *p, size_t n)
 {
    mp_err err = MP_ERR;
+#ifdef BN_S_READ_ARC4RANDOM_C
    if ((err != MP_OKAY) && MP_HAS(S_READ_ARC4RANDOM)) err = s_read_arc4random(p, n);
+#endif
+#ifdef BN_S_READ_WINCSP_C
    if ((err != MP_OKAY) && MP_HAS(S_READ_WINCSP))     err = s_read_wincsp(p, n);
+#endif
+#ifdef BN_S_READ_GETRANDOM_C
    if ((err != MP_OKAY) && MP_HAS(S_READ_GETRANDOM))  err = s_read_getrandom(p, n);
+#endif
+#ifdef BN_S_READ_URANDOM_C
    if ((err != MP_OKAY) && MP_HAS(S_READ_URANDOM))    err = s_read_urandom(p, n);
+#endif
+#ifdef BN_S_S_READ_LTM_RNG_C
    if ((err != MP_OKAY) && MP_HAS(S_READ_LTM_RNG))    err = s_read_ltm_rng(p, n);
+#endif
    return err;
 }