Update Tools necessary for Composite (missing/obsolete python)

[luisalfonsopreciado]

Summary of this Pull Request (PR)

Updated tools necessary for composite in doc/README.md

Intent for your PR

Update tools necessary for Composite.

I have gotten this error several times when setting up environment after running ./cos build:

/bin/sh: 1: gdb: not found
cd composer/ ; cargo build
/bin/sh: 1: cargo: not found
make: *** [Makefile:14: composer] Error 127
make: Leaving directory '/home/ubuntu/composite/src'

After installing:

sudo apt-get -y install cargo
sudo apt-get -y install gdb

I am able to ./cos build successfully.

Choose one (Mandatory):

• [X] This PR is for a code-review and is intended to get feedback, but not to be pulled yet.
• [ ] This PR is mature, and ready to be integrated into the repo.

Reviewers (Mandatory):

@gparmer

Code Quality

As part of this pull request, I've considered the following:

Style:

• [X] Comments adhere to the Style Guide (SG)
• [X] Spacing adhere's to the SG
• [X] Naming adhere's to the SG
• [X] All other aspects of the SG are adhered to, or exceptions are justified in this pull request
• [X] I have run the auto formatter on my code before submitting this PR (see doc/auto_formatter.md for instructions)

Code Craftsmanship:

• [X] I've made an attempt to remove all redundant code
• [X] I've considered ways in which my changes might impact existing code, and cleaned it up
• [X] I've formatted the code in an effort to make it easier to read (proper error handling, function use, etc...)
• [X] I've commented appropriately where code is tricky
• [X] I agree that there is no "throw-away" code, and that code in this PR is of high quality

Testing

I've tested the code using the following test programs (provide list here):

• [ ] micro_booter
• [ ] unit_pingpong
• [ ] unit_schedtests

[gparmer]

I worry about using apt-get to install cargo as it seems like much of the rust world uses rustup to install and update. (See https://doc.rust-lang.org/cargo/getting-started/installation.html). I can only imagine this would conflict with that? Maybe just include this instead:

curl https://sh.rustup.rs -sSf | sh

[luisalfonsopreciado]

I worry about using apt-get to install cargo as it seems like much of the rust world uses rustup to install and update. (See https://doc.rust-lang.org/cargo/getting-started/installation.html). I can only imagine this would conflict with that? Maybe just include this instead:

curl https://sh.rustup.rs -sSf | sh

Sounds reasonable, updated commit.