Version Used:
dotnet --version 2.1.200
macOS 10.13.4

Steps to Reproduce:

1. dotnet restore
2. dotnet build

.csproj
TargetFramework = netcoreapp1.1
PreserveCompilationContext = true
OutputType = Exe
RuntimeFrameworkVersion = 1.1.0
PackageTargetFallback = $(PackageTargetFallback);dotnet5.6;portable-net45+win8

Expected Behavior:
Build SUCCESS.

Actual Behavior:
Build FAILED.

/usr/local/share/dotnet/sdk/2.1.200/Roslyn/Microsoft.CSharp.Core.targets(52,5): error MSB6006: "csc.dll" exited with code 134. [/Users/xyz/Documents/Github/xyz/src/xyz/xyz.csproj]
0 Warning(s)
1 Error(s)