test(compiler-cli): fix drive letter casing in Windows filesystem emulation (#37782)

In native windows, the drive letter is a capital letter, while our Windows
filesystem emulation would use lowercase drive letters. This difference may
introduce tests to behave differently in native Windows versus emulated
Windows, potentially causing unexpected CI failures on Windows CI after a PR
has been merged.

Resolves FW-2267

PR Close #37782

packages/compiler-cli/src/ngtsc/file_system/testing/src/mock_file_system_windows.ts

@@ -42,6 +42,6 @@ export class MockFileSystemWindows extends MockFileSystem {
   }
 
   normalize<T extends PathString>(path: T): T {
-    return path.replace(/^[\/\\]/i, 'c:/').replace(/\\/g, '/') as T;
+    return path.replace(/^[\/\\]/i, 'C:/').replace(/\\/g, '/') as T;
   }
 }