Trim LF from EmscriptenVersion and EmscriptenRevision variables

[yamachu]

Thanks to #393 , it is now possible to reference EmscriptenVersion from csproj and similar files.
This allows referencing the appropriate wasm file for the runtime version within a nuget package.
e.g. https://github.com/yamachu/SharpOpenJTalk/blob/d98afa9f11f9c780f63750ae1ba7c31d9e21097c/library/lang/nuget/SharpOpenJTalk.Lang.props#L10

However, since a line feed (LF, 0x0a) character exists at the end of the file, the variable becomes difficult to use unless Trim is applied.
Therefore, I have modified the code to trim the variable at the point where it is defined, making it more intuitive and easier for users to handle.

$ cat /usr/local/share/dotnet/packs/Microsoft.NET.Runtime.Emscripten.3.1.56.Sdk.osx-arm64/10.0.1/tools/emscripten/emscripten-version.txt|xxd
00000000: 2233 2e31 2e35 3622 0a                   "3.1.56".
$ cat /usr/local/share/dotnet/packs/Microsoft.NET.Runtime.Emscripten.3.1.56.Sdk.osx-arm64/10.0.1/tools/emscripten/emscripten-revision.txt|xxd
00000000: 3537 6232 3162 3866 6463 6265 3365 6262  57b21b8fdcbe3ebb
00000010: 3532 3331 3738 6237 3934 3635 3235 3436  523178b794652546
00000020: 3638 6561 6234 3038 0a                   68eab408.