Added checks for main dependencies on runtime's build scripts

build.cmd

@@ -1,6 +1,8 @@
 @echo off
 setlocal
 
+call "%~dp0eng\vs_tools_check.cmd"
+
 set _args=%*
 if "%~1"=="-?" set _args=-help
 

eng/build.ps1

@@ -100,6 +100,32 @@ function Get-Help() {
   Write-Host "For more information, check out https://github.com/dotnet/runtime/blob/master/docs/workflow/README.md"
 }
 
+function Assert-InstalledDependency($dependencyName)
+{
+  try {
+    Get-Command -Name $dependencyName -ErrorAction Stop >$null 2>&1
+  }
+  catch {
+    Write-Host "$dependencyName is required to build this repo. Make sure to install it and try again."
+    Write-Host "For a full list of requirements, see https://github.com/dotnet/runtime/blob/master/docs/workflow/requirements/windows-requirements.md"
+    exit 1
+  }
+}
+
+function Assert-GitLongPathsEnabled()
+{
+  # This needs to be in a variable. Otherwise, Invoke-Command complains about
+  # an incompatible cast.
+  $gitscript = [scriptblock]::Create("git config --get core.longpaths")
+  $longpaths = Invoke-Command -scriptblock $gitscript
+
+  if (-Not $longpaths) {
+    Write-Host "Git Long Paths must be enabled to build this repo."
+    Write-Host "For a full list of requirements, see https://github.com/dotnet/runtime/blob/master/docs/workflow/requirements/windows-requirements.md"
+    exit 1
+  }
+}
+
 if ($help -or (($null -ne $properties) -and ($properties.Contains('/help') -or $properties.Contains('/?')))) {
   Get-Help
   exit 0
@@ -110,6 +136,10 @@ if ($subset -eq 'help') {
   exit 0
 }
 
+Assert-InstalledDependency("CMake")
+Assert-InstalledDependency("Git")
+Assert-GitLongPathsEnabled
+
 if ($vs) {
   . $PSScriptRoot\common\tools.ps1
 

eng/build.sh

@@ -136,6 +136,21 @@ showSubsetHelp()
   "$scriptroot/common/build.sh" "-restore" "-build" "/p:Subset=help" "/clp:nosummary"
 }
 
+assertInstalledDependency()
+{
+  dependency="$(echo "$1" | awk '{print tolower($0)}')"
+  location="$(command -v $dependency)"
+
+  if [ -z "$location" ]; then
+    echo "$dependency is required to build this repo. Make sure to install it and try again."
+    echo "For a full list of requirements, see https://github.com/dotnet/runtime/blob/master/docs/workflow/requirements/linux-requirements.md"
+    exit 1
+  fi
+}
+
+assertInstalledDependency 'CMake'
+assertInstalledDependency 'Git'
+
 arguments=''
 cmakeargs=''
 extraargs=''

eng/vs_tools_check.cmd

@@ -0,0 +1,40 @@
+@if not defined _echo @echo off
+
+REM This script checks and ensures there is a working Visual Studio installation
+REM alongside its dev tools. This is a requirement to build the runtime repo.
+REM All passed arguments are ignored
+REM Script will return 0 if a VS installation is found, and 1 if any problems
+REM cause it to fail.
+
+:: Default to highest Visual Studio version available
+
+:: For VS2017 and later, multiple instances can be installed on the same box.
+:: SxS and VS1*0COMNTOOLS are no longer set as global environment variables and
+:: are instead only set if the user has launched the Visual Studio Developer
+:: Command Prompt.
+
+:: Following this logic, we will default to the Visual Studio toolset associated
+:: with the active Developer Command Prompt. Otherwise, we will query VSWhere to
+:: locate the later version of Visual Studio available on the machine. Finally,
+:: we will fail the script if not supported instance can be found.
+
+if defined VisualStudioVersion (
+    goto skip_setup
+)
+
+set _VSWHERE="%ProgramFiles(x86)%\Microsoft Visual Studio\Installer\vswhere.exe"
+if exist %_VSWHERE% (
+    for /f "usebackq tokens=*" %%i in (`%_VSWHERE% -latest -prerelease -property installationPath`) do set _VSCOMNTOOLS=%%i\Common7\Tools
+    goto call_vs
+)
+
+:call_vs
+if not exist "%_VSCOMNTOOLS%" (
+    echo %__MsgPrefix%Error: Visual Studio 2019 is required to build this repo. Make sure to install it and try again.
+    echo For a full list of requirements, see https://github.com/dotnet/runtime/blob/master/docs/workflow/requirements/windows-requirements.md
+    exit /b 1
+)
+
+:skip_setup
+
+exit /b 0