Added checks for main dependencies on runtime's build scripts

build.cmd

@@ -1,6 +1,12 @@
 @echo off
 setlocal
 
+:: Call setup_vs_tools with the '1' flag to tell it to only check for the
+:: VS installation, and not launch the Dev Prompt. More details are in that
+:: script source file.
+
+call "%~dp0src\coreclr\setup_vs_tools.cmd" 1
+
 set _args=%*
 if "%~1"=="-?" set _args=-help
 if "%~1"=="/?" set _args=-help

eng/build.ps1

@@ -106,6 +106,18 @@ 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 "$dependencyName is required to build this repo. Make sure to install it and try again."
+    Write-Host "For a full list of requirements, see https://github.com/dotnet/runtime/blob/master/docs/workflow/requirements/windows-requirements.md"
+    exit 1
+  }
+}
+
 if ($help) {
   Get-Help
   exit 0
@@ -116,6 +128,8 @@ if ($subset -eq 'help') {
   exit 0
 }
 
+Assert-InstalledDependency("Git")
+
 if ($vs) {
   . $PSScriptRoot\common\tools.ps1
 

eng/build.sh

@@ -144,6 +144,21 @@ 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=''

src/coreclr/setup_vs_tools.cmd

@@ -16,6 +16,19 @@ REM vs2017 or vs2019
 :: Visual Studio available on the machine. Finally, we will fail the script if not supported
 :: instance can be found.
 
+:: This script is also called by the main build.cmd, located at the root of the
+:: runtime repo. For this specific scenario, we want to check if there is a
+:: valid VS installation, but not call the Developer Command Prompt. For this
+:: purpose, we pass a flag labelled as the number '1' from said script and store
+:: it in this variable "__VSOnlyCheck". This is then checked at the end to define
+:: whether or not to call the VS Dev Prompt.
+::
+:: The original CoreCLR callers within this directory remain untouched. In this
+:: case, they don't pass any flags and so since "__VSOnlyCheck" will be undefined
+:: in those cases, execution will proceed as normally.
+
+set __VSOnlyCheck=%1
+
 if defined VisualStudioVersion (
     if not defined __VSVersion echo %__MsgPrefix%Detected Visual Studio %VisualStudioVersion% developer command ^prompt environment
     goto skip_setup
@@ -34,6 +47,12 @@ if not exist "%_VSCOMNTOOLS%" (
     echo        Please see https://github.com/dotnet/runtime/blob/master/docs/workflow/requirements/windows-requirements.md for build instructions.
     exit /b 1
 )
+
+:: If called from runtime's build.cmd, we are done here and thus we proceed
+:: to the exit.
+
+if "%__VSOnlyCheck%" == "1" goto :skip_setup
+
 echo %__MsgPrefix%"%_VSCOMNTOOLS%\VsDevCmd.bat"
 call "%_VSCOMNTOOLS%\VsDevCmd.bat"