bpo-39930: Convert error to warning for more silent failure (GH-18921)

Makes it an error to create a layout without vcruntime DLL
(cherry picked from commit fde44ae6d0)

Co-authored-by: Steve Dower <steve.dower@python.org>

PC/layout/main.py

@@ -153,8 +153,12 @@ def get_layout(ns):
     if ns.include_stable:
         yield from in_build(PYTHON_STABLE_DLL_NAME)
 
+    found_any = False
     for dest, src in rglob(ns.build, "vcruntime*.dll"):
+        found_any = True
         yield dest, src
+    if not found_any:
+        log_error("Failed to locate vcruntime DLL in the build.")
 
     yield "LICENSE.txt", ns.source / "LICENSE"
 

PCbuild/pyproject.props

@@ -211,7 +211,7 @@ public override bool Execute() {
       <VCRuntimeDLL Include="$(VCRedistDir)\Microsoft.VC*.CRT\vcruntime*.dll" />
     </ItemGroup>
 
-    <Error Text="vcruntime14*.dll not found under $(VCInstallDir)" Condition="@(VCRuntimeDLL) == ''" />
+    <Warning Text="vcruntime14*.dll not found under $(VCInstallDir)" Condition="@(VCRuntimeDLL) == ''" />
     <Message Text="VCRuntimeDLL: @(VCRuntimeDLL)" Importance="high" />
   </Target>
 </Project>