make tool paths returned for the netcore host in line with full-framework

[baronfel]

even though FSAC is running on netcore, the tools it returns back should probably be full-framework compatible until we get to a spot where tooling can tell fsac where compilers/corelibs are.

This makes it so that non-windows, netcore users of FSAC get the same compiler binaries returned as non-windows, mono users of FSAC. This enables ionide to trust the responses received from FSAC instead of having to probe on its own.

Before (mono):

➜  bin git:(master) ✗ mono fsautocomplete.exe
compilerlocation
{"Kind":"compilerlocation","Data":{"Fsc":"fsharpc","Fsi":"fsharpi","MSBuild":"xbuild"}}

Before(netcore):

➜  bin_netcore git:(master) ✗ dotnet fsautocomplete.dll
compilerlocation
{"Kind":"compilerlocation","Data":{"Fsc":"fsc.exe","Fsi":"fsi.exe","MSBuild":"msbuild"}}

After(mono):

➜  bin git:(master) ✗ mono fsautocomplete.exe
compilerlocation
{"Kind":"compilerlocation","Data":{"Fsc":"fsharpc","Fsi":"fsharpi","MSBuild":"msbuild"}}

After(netcore):

➜  netcoreapp2.0 git:(netcore_binary_paths) ✗ dotnet fsautocomplete.dll
compilerlocation
{"Kind":"compilerlocation","Data":{"Fsc":"fsc.exe","Fsi":"fsharpi","MSBuild":"msbuild"}}

[baronfel]

@Krzysztof-Cieslak you got those firey fingers 👍 I'll integrate this update into the MR I'm working on for ionide