[llvm-ar][test] Relax lit directory assumptions in thin-archive.test

[rupprecht]

Summary

thin-archive.test assumes the Output/<testname> structure that lit creates. Rewrite the test in a way that still tests the same thing (creating via relative path and adding via absolute path) but doesn't assume this specific lit structure, making it possible to run in a lit emulator.

[gbreynoo]

LGTM

llvm/trunk/test/tools/llvm-ar/thin-archive.test

 RUN: rm -rf %t && mkdir -p %t/foo/bar/
 
 RUN: yaml2obj %S/Inputs/elf.yaml -o %t/foo/elf.o
 RUN: cp %t/foo/elf.o %t/foo/bar/elf.o
 RUN: cp %t/foo/bar/elf.o %t/delete.o
 
 Test that modules can be added with absolute paths when the archive is created using an absolute path
 
 RUN: llvm-ar rTc %t/absolute-1.ar %t/foo/elf.o %t/delete.o %t/foo/bar/elf.o
 RUN: llvm-ar dT %t/absolute-1.ar delete.o
 
 RUN: FileCheck -input-file=%t/absolute-1.ar --check-prefixes=THIN,CHECK %s -DPATH=%/t/
 RUN: llvm-ar t %t/absolute-1.ar | FileCheck %s -DPATH=%/t/
 
-Test that modules can be added with absolute paths when the archive is created using a relative path
+These tests must be run in %t/foo. cd %t is included on each line to make debugging this test case easier.
 
-RUN: llvm-ar rTc Output/%basename_t.tmp/absolute-2.ar %t/foo/elf.o %t/delete.o %t/foo/bar/elf.o
-RUN: llvm-ar dT Output/%basename_t.tmp/absolute-2.ar %t/delete.o
+Test that modules can be added with absolute paths when the archive is created using a relative path
 
-RUN: FileCheck -input-file=%t/absolute-2.ar --check-prefixes=THIN,CHECK %s -DPATH=%/t/
-RUN: llvm-ar t %t/absolute-2.ar | FileCheck %s -DPATH=%/t/
+RUN: cd %t/foo && llvm-ar rTc bar/absolute-2.ar %t/foo/elf.o %t/delete.o %t/foo/bar/elf.o
+RUN: cd %t/foo && llvm-ar dT bar/absolute-2.ar %t/delete.o
 
-These tests must be run in %t/foo. cd %t is included on each line to make debugging this test case easier.
+RUN: FileCheck -input-file=%t/foo/bar/absolute-2.ar --check-prefixes=THIN,CHECK %s -DPATH=%/t/
+RUN: llvm-ar t %t/foo/bar/absolute-2.ar | FileCheck %s -DPATH=%/t/
 
 Test that modules can be added with relative paths when the archive is created using a relative path
 
 RUN: cd %t/foo && llvm-ar rTc ../relative-1.ar elf.o ../delete.o bar/elf.o
 RUN: cd %t/foo && llvm-ar dT ../relative-1.ar delete.o
 
 RUN: FileCheck -input-file=%t/relative-1.ar --check-prefixes=THIN,CHECK %s -DPATH=
 RUN: llvm-ar t %t/relative-1.ar | FileCheck %s -DPATH=%/t/