[NFC] [tests] Don't try to remove and create the same directory

In the test of
clang/test/Modules/no-transitive-source-location-change.cppm, there were
reports about invalid directory names in windows. The reason may be that
we may remove and create the same directory. This patch tries to avoid
such patterns for that.

Author: ChuanqiXu9

clang/test/Modules/no-transitive-source-location-change.cppm

@@ -3,7 +3,6 @@
 //
 // RUN: rm -rf %t
 // RUN: split-file %s %t
-// RUN: cd %t
 //
 // RUN: %clang_cc1 -std=c++20 %t/A.cppm -emit-module-interface -o %t/A.pcm
 // RUN: %clang_cc1 -std=c++20 %t/A.v1.cppm -emit-module-interface -o %t/A.v1.pcm
@@ -25,10 +24,6 @@
 // RUN:     -o %t/C.v1.pcm
 // RUN: not diff %t/C.v1.pcm %t/C.pcm  &> /dev/null
 //
-// RUN: rm -rf %t
-// RUN: split-file %s %t
-// RUN: cd %t
-//
 // Test again with reduced BMI.
 // RUN: %clang_cc1 -std=c++20 %t/A.cppm -emit-reduced-module-interface -o %t/A.pcm
 // RUN: %clang_cc1 -std=c++20 %t/A.v1.cppm -emit-reduced-module-interface -o %t/A.v1.pcm