Enable strip binary on release build

[MiSawa]

This PR is to enable stripping option on the release build of the generated cargo project. Resolves #36

Comparison of built binary

It actually works, and the binary size of a hello world program reduced from 3.5M to 300K.

$ ./rust-script-no-strip --clear-cache ./hello.rs
Hello world!
$ file $binary
/home/misawa/.cache/rust-script/binaries/release/hello_59500b17925d6a21fe59ae0b: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=da41165504c484ad9734ded644b275ae7d4c2030, for GNU/Linux 4.4.0, with debug_info, not stripped
$ du $binary
3.5M    /home/misawa/.cache/rust-script/binaries/release/hello_59500b17925d6a21fe59ae0b
$ ./rust-script-with-strip --clear-cache ./hello.rs
Hello world!
$ file $binary
/home/misawa/.cache/rust-script/binaries/release/hello_59500b17925d6a21fe59ae0b: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=558091b50cb49c7c88877998d454b9bda928a973, for GNU/Linux 4.4.0, stripped
$ du $binary
300K    /home/misawa/.cache/rust-script/binaries/release/hello_59500b17925d6a21fe59ae0b

Comparison of build+run time

I'd say they're the same.

$ hyperfine './rust-script-no-strip --clear-cache ./hello.rs' './rust-script-with-strip --clear-cache ./hello.rs' -w 10
Benchmark 1: ./rust-script-no-strip --clear-cache ./hello.rs
  Time (mean ± σ):      1.114 s ±  0.066 s    [User: 0.946 s, System: 0.180 s]
  Range (min … max):    1.050 s …  1.253 s    10 runs

Benchmark 2: ./rust-script-with-strip --clear-cache ./hello.rs
  Time (mean ± σ):      1.051 s ±  0.035 s    [User: 0.882 s, System: 0.186 s]
  Range (min … max):    1.006 s …  1.128 s    10 runs

Summary
  './rust-script-with-strip --clear-cache ./hello.rs' ran
    1.06 ± 0.07 times faster than './rust-script-no-strip --clear-cache ./hello.rs'

Compatibilities

Works fine (I mean, just a warning message that's shown only when you passed -o) when used with older version of cargo.

$ rustup default 1.42.0-x86_64-unknown-linux-gnu
info: using existing install for '1.42.0-x86_64-unknown-linux-gnu'
info: default toolchain set to '1.42.0-x86_64-unknown-linux-gnu'

  1.42.0-x86_64-unknown-linux-gnu unchanged - rustc 1.42.0 (b8cedc004 2020-03-09)

$ ./rust-script-with-strip --clear-cache -o ./hello.rs
warning: unused manifest key: profile.release.strip
   Compiling hello v0.1.0 (/home/misawa/.cache/rust-script/projects/59500b17925d6a21fe59ae0b)
    Finished release [optimized] target(s) in 0.79s
     Running `/home/misawa/.cache/rust-script/binaries/release/hello_59500b17925d6a21fe59ae0b`
Hello world!

Other consideration

I don't have Windows / Mac OSX, so unsure how it perform on those environment.

[fornwall]

Thanks! Will be included in version 0.21.0, which will be released shortly.