System.Text.Json is not inbox on netfx

[wtgodbe]

Fixes test build break introduced by 1743e47

Serialization\Value.ReadTests.cs(225,58): error CS0117: 'BitConverter' does not contain a definition for 'SingleToInt32Bits' [D:\a\1\s\src\System.Text.Json\tests\System.Text.Json.Tests.csproj]

corefx/src/System.Text.Json/tests/Serialization/Value.ReadTests.cs

Lines 224 to 227 in 30ca411

	// Verify sign is correct; SingleToInt32Bits not available on netfx.
	Assert.Equal(0x00000000u, (uint)BitConverter.SingleToInt32Bits(JsonSerializer.Parse<float>("0")));
	Assert.Equal(0x80000000u, (uint)BitConverter.SingleToInt32Bits(JsonSerializer.Parse<float>("-0")));
	Assert.Equal(0x80000000u, (uint)BitConverter.SingleToInt32Bits(JsonSerializer.Parse<float>("-0.0")));

These tests were failing on netfx, since System.Text.Json isn't inbox on that platform, but the ifdef wasn't catching that after we added netfx to the test configurations: https://github.com/dotnet/corefx/blame/master/src/System.Text.Json/tests/Configurations.props

CC @safern @ViktorHofer @ahsonkhan

[wtgodbe]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s), but failed to run 1 pipeline(s).

[ViktorHofer]

Thanks

[wtgodbe]

Test failures are either known outerloop issues, or known infra failures on MUSL.

[ViktorHofer]

@wtgodbe please use azp run only when you want to trigger Outerloop. In this case I guess you just wanted to retrigger CI which you can do by either push force your amended commit or retrigger via the AzDO checks page.