Imported Upstream version 5.4.0.167

Former-commit-id: 5624ac747d633e885131e8349322922b6a59baaa

external/corefx/Documentation/building/code-coverage.md

@@ -20,7 +20,7 @@ Our default, somewhat-arbitrary initial goal for a library is 90% code coverage.
 
 ## Issues
 
-Issues are opened for a library when a cursory examination of its code coverage reveal that there are likely still some meaningful gaps that need to be addressed.  We welcome contributions to our test suites to help address these gaps and close these issues.  Many of these issues are marked as "up for grabs".
+Issues are opened for a library when a cursory examination of its code coverage reveal that there are likely still some meaningful gaps that need to be addressed.  We welcome contributions to our test suites to help address these gaps and close these issues.  Many of these issues are marked as [up-for-grabs](https://github.com/dotnet/corefx/labels/up-for-grabs).
 
 An issue need not be addressed in its entirety.  We happily accept contributions that improve our tests and work towards improving code coverage numbers even if they only incrementally improve the situation.
 

external/corefx/Documentation/building/unix-instructions.md

@@ -57,6 +57,8 @@ most systems when you install the development packages).
 
 ### macOS
 
+macOS 10.12 or higher is needed to build corefx 2.x.
+
 On macOS a few components are needed which are not provided by a default developer setup:
 * CMake
 * pkgconfig

external/corefx/Documentation/building/windows-instructions.md

@@ -23,6 +23,8 @@ For Visual Studio 2017:
     * VC++ 2017 v141 Toolset (x86, x64)
     * Windows 8.1 SDK and UCRT SDK
     * VC++ 2015.3 v140 Toolset (x86, x64)
+  * .NET Core cross-platform development
+    * All Required Components
 * When doing an 'Individual Components' based install, the following are the minimum requirements:
   * C# and Visual Basic Roslyn Compilers
   * Static Analysis Tools