ignore casing when converting a source file path to relative path

Author: zhengbli

src/compiler/utilities.ts

@@ -2330,7 +2330,9 @@ namespace ts {
 
     export function getSourceFilePathInNewDir(sourceFile: SourceFile, host: EmitHost, newDirPath: string) {
         let sourceFilePath = getNormalizedAbsolutePath(sourceFile.fileName, host.getCurrentDirectory());
-        sourceFilePath = sourceFilePath.replace(host.getCommonSourceDirectory(), "");
+        const commonSourceDirectory = host.getCommonSourceDirectory();
+        const isSourceFileInCommonSourceDirectory = sourceFilePath.toLowerCase().indexOf(commonSourceDirectory.toLowerCase()) === 0;
+        sourceFilePath = isSourceFileInCommonSourceDirectory ? sourceFilePath.substring(commonSourceDirectory.length) : sourceFilePath;
         return combinePaths(newDirPath, sourceFilePath);
     }