Ensure crate is compiled with std for panic handler

This CL adds a patch to use `extern crate std` to ensure that a panic
handler is available when the crate is compiled as a dylib.

Test: m libpercent_encoding
Bug: 333887339
Change-Id: I38f91e3b99f483b0f248ac95ba1f6aaaa64762d0
2 files changed