bootstrap: some cleanup tweaks.

- Use Bash for nicer syntax below (`&>`)
- Don't need to set `CC` to `gcc`
- Ensure we're in the right path

Author: MikeMcQuaid

script/bootstrap

@@ -1,10 +1,11 @@
-#!/bin/sh
+#!/bin/bash
 
 set -e
-export CC=gcc
+
+cd "$(dirname "$0")/.."
 
 echo "==> Installing gem dependencies…"
-bundle check --path vendor/gems 2>&1 > /dev/null || {
+bundle check --path vendor/gems &>/dev/null || {
   time bundle install --binstubs bin --path vendor/gems
 }