Apply fixes from shellcheck

[Mic92]

bors merge

[bors[bot]]

Build succeeded:

• Build static musl binaries (amd64)
• Build static musl binaries (arm32v7)
• Build static musl binaries (arm64v8)
• Build static musl binaries (i386)
• Build static musl binaries (ppc64le)
• Build static musl binaries (riscv64)
• Build static musl binaries (s390x)
• Build tarballs
• Build windows executable
• nix
• Test windows binaries
• ubuntu