apps: Remove pivot_root

This functionality is intended to be used only by preinit, so it doesn't make sense to make it a command-line utility.

apps/CMakeLists.txt

@@ -35,7 +35,6 @@ luna_app(time.cpp time)
 luna_app(ln.cpp ln)
 luna_app(mktemp.cpp mktemp)
 luna_app(sysfuzz.cpp sysfuzz)
-luna_app(pivot_root.cpp pivot_root)
 luna_app(cp.cpp cp)
 luna_app(kill.cpp kill)
 luna_app(gol.cpp gol)

apps/pivot_root.cpp

@@ -1,19 +0,0 @@
-#include <os/ArgumentParser.h>
-#include <sys/syscall.h>
-#include <unistd.h>
-
-Result<int> luna_main(int argc, char** argv)
-{
-    StringView new_root;
-    StringView put_old;
-
-    os::ArgumentParser parser;
-    parser.add_description("Move the current root directory to another directory and replace it with another mount.");
-    parser.add_system_program_info("pivot_root"_sv);
-    parser.add_positional_argument(new_root, "new_root", true);
-    parser.add_positional_argument(put_old, "put_old", true);
-    parser.parse(argc, argv);
-
-    long rc = syscall(SYS_pivot_root, new_root.chars(), put_old.chars());
-    return Result<int>::from_syscall(rc);
-}