grunt - fix grunt.file.expand errors (#29299)

- patterns can be a string or a string array
- options can have a 'cwd' property

types/grunt/grunt-tests.ts

@@ -133,4 +133,9 @@ exports.exports = function(grunt: IGrunt) {
 let myTest = function (grunt: IGrunt) {
     grunt.file.expand(['*.ts']);
     grunt.file.expand('*.ts');
+
+    // 'cwd' in options, and string pattern
+    grunt.file.expand({
+        cwd: '.'
+    }, '*.ts');
 }

types/grunt/index.d.ts

@@ -446,7 +446,7 @@ declare namespace grunt {
              * grunt.file.setBase or the --base command-line option.
              */
             expand(patterns: string | string[]): string[];
-            expand(options: IFilesConfig, patterns: string[]): string[];
+            expand(options: IFilesConfig, patterns: string | string[]): string[];
 
             /**
              * Returns an array of src-dest file mapping objects.
@@ -595,6 +595,12 @@ declare namespace grunt {
             // filter?: string
             // filter?: (src: string) => boolean
             filter?: any;
+
+            /**
+             * Patterns will be matched relative to this path, and all returned filepaths will
+             * also be relative to this path.
+             */
+            cwd?: string;
         }
 
         /**