selftests/nolibc: chdir_root: restore current path after test

The PWD environment variable has the path of the nolibc-test program,
the current path must be the same as it, otherwise, the test cases will
fail with relative path (e.g. ./nolibc-test).

Since only chdir_root really changes the current path, let's restore it
with the PWD environment variable.
Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>

tools/testing/selftests/nolibc/nolibc-test.c

@@ -703,7 +703,7 @@ int run_syscall(int min, int max)
 		CASE_TEST(sbrk_0);            EXPECT_PTRNE(1, sbrk(0), (void *)-1); break;
 		CASE_TEST(sbrk);              if ((p1 = p2 = sbrk(4096)) != (void *)-1) p2 = sbrk(-4096); EXPECT_SYSZR(1, (p2 == (void *)-1) || p2 == p1); break;
 		CASE_TEST(brk);               EXPECT_SYSZR(1, brk(sbrk(0))); break;
-		CASE_TEST(chdir_root);        EXPECT_SYSZR(1, chdir("/")); break;
+		CASE_TEST(chdir_root);        EXPECT_SYSZR(1, chdir("/")); chdir(getenv("PWD")); break;
 		CASE_TEST(chdir_dot);         EXPECT_SYSZR(1, chdir(".")); break;
 		CASE_TEST(chdir_blah);        EXPECT_SYSER(1, chdir("/blah"), -1, ENOENT); break;
 		CASE_TEST(chmod_net);         EXPECT_SYSZR(proc, chmod("/proc/self/net", 0555)); break;