Move required linux packages into pre-build script

.pipelines/templates/build.yml

@@ -74,13 +74,6 @@ stages:
 
     - template: steps/full-checkout.yml
 
-    - task: Bash@3
-      condition: and(succeeded(), eq(variables['osName'], 'linux'))
-      inputs:
-        targetType: 'inline'
-        script: sudo apt-get update && sudo apt-get install -y nasm
-      displayName: 'Install Required Linux Package: nasm'
-
     - pwsh: |
         ./build-package.ps1 -PackageName "${{ parameters.packageName }}" -StagedArtifactsPath "$(Build.ArtifactStagingDirectory)/package"
       displayName: 'Run: install & stage (preconfigured)'

README.md

@@ -36,10 +36,4 @@ It does the following:
 ### Testing Linux Builds Locally
 Linux builds can be developed and run from Windows via WSL.  The ffmpeg-cloud pre-configured package for example was created using Ubuntu, which is the default WSL OS.
 
-A few system packages are required to run the powershell `build-package.ps1` script, specifically `clang` (or a similar compiler) and `pkg-config`.  Some pre-configured builds require additional packages, such as ffmpeg-cloud needing `nasm`.  You can install them via:
-```
-sudo apt update
-sudo apt install clang, pkg-config, nasm
-```
-
 Given that WSL is quite slow when reading / writing files between Linux and Windows, it's best to run builds directly within a Linux mounted file location (for example `~/projects/ThirdParty-Packages-vcpkg` instead of `/mnt/c/projects/ThirdParty-Packages-vcpkg`).

custom-steps/ffmpeg-cloud/pre-build.ps1

@@ -1,7 +1,30 @@
 Import-Module "$PSScriptRoot/../../scripts/ps-modules/Build" -DisableNameChecking
 
-if (-not (Get-IsOnMacOS)) {
-    exit
+if (Get-IsOnMacOS) {
+    Write-Message "Installing nasm..."
+    brew install nasm
+}
+
+if (Get-IsOnLinux) {
+    Write-Message "Verifying required packages are installed..."
+
+    $isClangMissing = -not(dpkg-query -W -f='${Status}' clang 2>/dev/null | Select-String "install ok installed");
+    $isPkgConfigMissing = -not(dpkg-query -W -f='${Status}' pkg-config 2>/dev/null | Select-String "install ok installed");
+    $isNasmMissing = -not(dpkg-query -W -f='${Status}' nasm 2>/dev/null | Select-String "install ok installed");
+
+    if ($isClangMissing -or $isPkgConfigMissing -or $isNasmMissing) {
+        sudo apt-get update
+    }
+
+    if ($isClangMissing) {
+        sudo apt-get install -y clang
+    }
+
+    if ($isPkgConfigMissing) {
+        sudo apt-get install -y pkg-config
+    }
+
+    if ($isNasmMissing) {
+        sudo apt-get install -y nasm
+    }
 }
-Write-Message "Installing nasm..."
-brew install nasm