Prevent accidental command execution in build script

Created by: helaan

In shellscript, backticks cause code evaluation. We don't want that here. There are two ways to solve this: wrap the string in single quotes which prevent evaluation or escape the backticks. However the former is flagged by Shellcheck as SC2016, while the latter is not flagged at all and in my opinion is clearer to those reading the code.

Test plan: I've tested it locally (my pc does not have musl-gcc installed, as it wasn't in the dependency list). CI should pass as well.