testing: force pwd to not resolve symlink

Looking for a ~universal command that will succeed regardless which
system this test is run on. pwd will resolve symlinks by default in some
cases.

src/Command.zig

@@ -700,7 +700,7 @@ test "Command: custom working directory" {
         .cwd = "C:\\Windows\\System32",
     } else .{
         .path = "/bin/sh",
-        .args = &.{ "/bin/sh", "-c", "pwd" },
+        .args = &.{ "/bin/sh", "-c", "pwd", "-L" },
         .stdout = stdout,
         .cwd = "/bin",
     };