[arm64][msvc] remove signbit ambiguity

MSVC 19.25 complains about signbit being ambiguous between
signbit(float) and signbit(double) overloads when called with an int8_t.
To remove the ambiguity, cast to a double.

Change-Id: I698f05eed9248eef493bbe46b75fcd07e37e2a05
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2118510Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Richard Townsend <richard.townsend@arm.com>
Cr-Commit-Position: refs/heads/master@{#66856}

test/cctest/wasm/test-run-wasm-simd.cc

@@ -1677,7 +1677,7 @@ WASM_SIMD_TEST_NO_LOWERING(I8x16BitMask) {
   FOR_INT8_INPUTS(x) {
     int32_t actual = r.Call(x);
     // Lane 0 is always 0 (positive), lane 1 is always -1.
-    int32_t expected = std::signbit(x) ? 0xFFFE : 0x0002;
+    int32_t expected = std::signbit(static_cast<double>(x)) ? 0xFFFE : 0x0002;
     CHECK_EQ(actual, expected);
   }
 }
@@ -1697,7 +1697,7 @@ WASM_SIMD_TEST_NO_LOWERING(I16x8BitMask) {
   FOR_INT16_INPUTS(x) {
     int32_t actual = r.Call(x);
     // Lane 0 is always 0 (positive), lane 1 is always -1.
-    int32_t expected = std::signbit(x) ? 0xFE : 2;
+    int32_t expected = std::signbit(static_cast<double>(x)) ? 0xFE : 2;
     CHECK_EQ(actual, expected);
   }
 }
@@ -1717,7 +1717,7 @@ WASM_SIMD_TEST_NO_LOWERING(I32x4BitMask) {
   FOR_INT32_INPUTS(x) {
     int32_t actual = r.Call(x);
     // Lane 0 is always 0 (positive), lane 1 is always -1.
-    int32_t expected = std::signbit(x) ? 0xE : 2;
+    int32_t expected = std::signbit(static_cast<double>(x)) ? 0xE : 2;
     CHECK_EQ(actual, expected);
   }
 }