fix(osinstaller): warn when checksums file is missing or incomplete for custom versions

When a version file is present but the checksums file is missing or lacks an entry
for the current platform, log a warning to make the unverified download visible rather
than silently skipping verification.

Author: wterpstra

src/main/osinstaller/CxInstaller.ts

@@ -79,7 +79,11 @@ export class CxInstaller {
             try {
                 const content = await fsPromises.readFile(this.getChecksumsFilePath(), 'utf-8');
                 checksum = (JSON.parse(content) as Record<string, string>)[key] ?? null;
+                if (checksum === null) {
+                    logger.warn(`No checksum found for ${key} in checksums file. Download will not be verified.`);
+                }
             } catch {
+                logger.warn(`Checksums file not found. Download of version ${version} will not be verified.`);
                 checksum = null;
             }
         }