readme: update the "Getting Started" section
A Unix/Linux OS and `bash` are prerequisites to build Firecracker
using the `tools/devtool` script.
@@ -39,8 +39,8 @@ To get started with Firecracker, download the latest
[release](https://github.com/firecracker-microvm/firecracker/releases) binaries
or build it from source.
-You can build Firecracker on any system that has Docker running (we use a
-development container) as follows:
+You can build Firecracker on any Unix/Linux system that has Docker running
+(we use a development container) and `bash` installed, as follows:
```bash
git clone https://github.com/firecracker-microvm/firecracker
