Removes usage of DOTNET_HOME in CLI repo.

[TheRealPiotrP]

DOTNET_HOME is no longer required, though it is a documented override, so this change removes all unnecessary references to DOTNET_HOME from the CLI Repo.

/cc @brthor @gkhanna79 @schellap @Sridhar-MS @robmen @davidfowl

[schellap]

In corehost.md

Runtime resolution is controlled by these environment variables:

• DOTNET_RUNTIME_SERVICING -> Global override for runtime
• DOTNET_PACKAGES_CACHE -> Secondary cache
• DOTNET_PACKAGES -> Package restore location

The runtime is located by searching the following paths in order, where APP_BASE refers to the directory containing the managed application assembly and LIBCORECLR refers to the platform-specific name for the CoreCLR library (libcoreclr.so on Unix, libcoreclr.dylib on Mac OS X, coreclr.dll on Windows). The first path that matches is used as the path to load the CoreCLR from.

• $DOTNET_RUNTIME_SERVICING/runtime/coreclr/LIBCORECLR
• $DOTNET_PACKAGES_CACHE/<Package Id>/<Package Version>/runtimes/<RID>/native/LICORECLR
• APP_BASE/LIBCORECLR
• $DOTNET_PACKAGES/<Package Id>/<Package Version>/runtimes/<RID>/native/LIBCORECLR
• On Unix:
  • /usr/local/share/dotnet/runtime/coreclr/LIBCORECLR [1]
  • /usr/share/dotnet/runtime/coreclr/LIBCORECLR
• On Windows:
  • %LocalAppData%\dotnet\runtime\coreclr\LIBCORECLR
  • %ProgramFiles%\dotnet\runtime\coreclr\LIBCORECLR [2]

[schellap]

How come you have lesser files? I have these...

        modified:   Documentation/manpages/dotnet-compile.1
        modified:   Documentation/manpages/dotnet-run.1
        modified:   Documentation/manpages/dotnet.1
        modified:   Documentation/specs/corehost.md
        modified:   README.md
        modified:   packaging/windows/registrykeys.wxs
        modified:   scripts/common/_common.ps1
        modified:   scripts/common/_common.sh
        modified:   scripts/common/_utility.ps1
        modified:   scripts/run-build.ps1
        modified:   scripts/run-build.sh
        modified:   src/corehost/cli/args.cpp
        modified:   src/corehost/cli/args.h
        modified:   src/dotnet/README.md
        modified:   src/dotnet/commands/dotnet-compile-csc/README.md
        modified:   src/dotnet/commands/dotnet-compile/README.md
        modified:   src/dotnet/commands/dotnet-run/README.md
        modified:   src/dotnet/commands/dotnet-run/RunCommand.cs

[bricelam]

Nuts. I was going to use this in dotnet/efcore#4602 to find the location of dotnet.exe from dotnet-ef. See the conversation in #1150.

[schellap]

LGTM. There are a couple of uses in the corehost cpp files, but they are only useful for internal purposes.

[TheRealPiotrP]

@bricelam you just made me very glad I did this PR today :)

take a look at src/Microsoft.Dotnet.Cli.Utils/CoreHost.cs

[brthor]

LGTM