Add x64 native tools to documentation (for usage)

After dotnet new and dotnet restore (which appear to work fine, as does dotnet run), I get an error doing a native compile:

PS C:\users\Public\hello-world> dotnet compile --native
Compiling hello-world for DNXCore,Version=v5.0

Compilation succeeded.
    0 Warning(s)
    0 Error(s)

Time elapsed 00:00:01.8077755
Input Assembly: C:\users\Public\hello-world\bin\Debug\dnxcore50\hello-world.dll
LINK : fatal error LNK1104: cannot open file 'kernel32.lib'
Linking of intermediate files failed.

And with -c Release as suggested here https://github.com/dotnet/cli/issues/633

PS C:\users\Public\hello-world> dotnet compile --native -c Release
Compiling hello-world for DNXCore,Version=v5.0

Compilation succeeded.
    0 Warning(s)
    0 Error(s)

Time elapsed 00:00:01.8150396
Input Assembly: C:\users\Public\hello-world\bin\Release\dnxcore50\hello-world.dll
LINK : fatal error LNK1181: cannot open input file 'kernel32.lib'
Linking of intermediate files failed.

Installed just now from https://dotnetcli.blob.core.windows.net/dotnet/dev/Binaries/Latest/dotnet-win-x64.latest.zip

Environment:

PS C:\users\Public\hello-world> dotnet --version
.NET Command Line Tools (1.0.0)
Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.10586
 OS Platform: Windows
 Runtime Id:  win10-x64

[brthor]

Are you inside VS 2015 x64 Native Tools command prompt? This is currently a requirement for Native Compilation.

[blackdwarf]

We need to document the fact that you need to run the native compilation within a certain context (cmd prompt).