Add trivial expm1 test for SYCL functionality

test/sycl_jamfile

@@ -18,3 +18,4 @@ run test_beta_simple.cpp ;
 run test_cbrt.cpp ;
 run test_sign.cpp ;
 run test_round.cpp ;
+run test_expm1_simple.cpp;

test/test_expm1_simple.cpp

@@ -0,0 +1,32 @@
+//  Copyright Matt Borland 2024.
+//  Use, modification and distribution are subject to the
+//  Boost Software License, Version 1.0. (See accompanying file
+//  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#include <random>
+#include <cmath>
+#include <boost/math/special_functions/expm1.hpp>
+#include "math_unit_test.hpp"
+
+constexpr int N = 50000;
+
+template <typename T>
+void test()
+{
+    std::mt19937_64 rng(42);
+    std::uniform_real_distribution<T> dist(0, 0.01);
+
+    for (int n = 0; n < N; ++n)
+    {
+        const T value (dist(rng));
+        CHECK_ULP_CLOSE(std::expm1(value), boost::math::expm1(value), 10);
+    }
+}
+
+int main()
+{
+    test<float>();
+    test<double>();
+
+    return boost::math::test::report_errors();
+}