figlet: simplify, enable tests, fix for cross and musl

[dtzWill]

• Tested using sandboxing (nix.useSandbox on NixOS, or option build-use-sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.

---

[GrahamcOfBorg]

Success on aarch64-linux (full log)

Partial log (click to expand)

shrinking /nix/store/yg15zq7crqwb5dh0qarq2bmh11cs10bd-figlet-2.2.5/bin/chkfont
shrinking /nix/store/yg15zq7crqwb5dh0qarq2bmh11cs10bd-figlet-2.2.5/bin/figlet
gzipping man pages under /nix/store/yg15zq7crqwb5dh0qarq2bmh11cs10bd-figlet-2.2.5/share/man/
strip is /nix/store/xmpjypwjmp2qi1chs5kr0hacnh161ls4-binutils-2.28.1/bin/strip
stripping (with command strip and flags -S) in /nix/store/yg15zq7crqwb5dh0qarq2bmh11cs10bd-figlet-2.2.5/bin
patching script interpreter paths in /nix/store/yg15zq7crqwb5dh0qarq2bmh11cs10bd-figlet-2.2.5
/nix/store/yg15zq7crqwb5dh0qarq2bmh11cs10bd-figlet-2.2.5/bin/showfigfonts: interpreter directive changed from "/bin/sh -" to "/nix/store/7fxbh1yhagvwbdrmdyyy5ghcjhwjndhs-bash-4.4-p12/bin/sh -"
/nix/store/yg15zq7crqwb5dh0qarq2bmh11cs10bd-figlet-2.2.5/bin/figlist: interpreter directive changed from "/bin/sh -" to "/nix/store/7fxbh1yhagvwbdrmdyyy5ghcjhwjndhs-bash-4.4-p12/bin/sh -"
checking for references to /build in /nix/store/yg15zq7crqwb5dh0qarq2bmh11cs10bd-figlet-2.2.5...
/nix/store/yg15zq7crqwb5dh0qarq2bmh11cs10bd-figlet-2.2.5

[GrahamcOfBorg]

Success on x86_64-darwin (full log)

Partial log (click to expand)

cp fonts/*.flc /nix/store/v4gvrmy3h1gcczsp0w498nl9jbsap8ra-figlet-2.2.5/share/figlet
post-installation fixup
moving /nix/store/v4gvrmy3h1gcczsp0w498nl9jbsap8ra-figlet-2.2.5/man to /nix/store/v4gvrmy3h1gcczsp0w498nl9jbsap8ra-figlet-2.2.5/share/man
gzipping man pages under /nix/store/v4gvrmy3h1gcczsp0w498nl9jbsap8ra-figlet-2.2.5/share/man/
strip is /nix/store/5a88zk3jgimdmzg8rfhvm93kxib3njf9-cctools-binutils-darwin/bin/strip
stripping (with command strip and flags -S) in /nix/store/v4gvrmy3h1gcczsp0w498nl9jbsap8ra-figlet-2.2.5/bin
patching script interpreter paths in /nix/store/v4gvrmy3h1gcczsp0w498nl9jbsap8ra-figlet-2.2.5
/nix/store/v4gvrmy3h1gcczsp0w498nl9jbsap8ra-figlet-2.2.5/bin/figlist: interpreter directive changed from "/bin/sh -" to "/nix/store/s8mff1kmnc63b21ybdid2ni0fw7mzy7r-bash-4.4-p12/bin/sh -"
/nix/store/v4gvrmy3h1gcczsp0w498nl9jbsap8ra-figlet-2.2.5/bin/showfigfonts: interpreter directive changed from "/bin/sh -" to "/nix/store/s8mff1kmnc63b21ybdid2ni0fw7mzy7r-bash-4.4-p12/bin/sh -"
/nix/store/v4gvrmy3h1gcczsp0w498nl9jbsap8ra-figlet-2.2.5

[GrahamcOfBorg]

Success on x86_64-linux (full log)

Partial log (click to expand)

shrinking /nix/store/j45p7ifxr64s38zmrdv1icx7fs2b9y14-figlet-2.2.5/bin/chkfont
shrinking /nix/store/j45p7ifxr64s38zmrdv1icx7fs2b9y14-figlet-2.2.5/bin/figlet
gzipping man pages under /nix/store/j45p7ifxr64s38zmrdv1icx7fs2b9y14-figlet-2.2.5/share/man/
strip is /nix/store/5qj61lcvzlap87rf6blvf8p577d482bv-binutils-2.28.1/bin/strip
stripping (with command strip and flags -S) in /nix/store/j45p7ifxr64s38zmrdv1icx7fs2b9y14-figlet-2.2.5/bin 
patching script interpreter paths in /nix/store/j45p7ifxr64s38zmrdv1icx7fs2b9y14-figlet-2.2.5
/nix/store/j45p7ifxr64s38zmrdv1icx7fs2b9y14-figlet-2.2.5/bin/figlist: interpreter directive changed from "/bin/sh -" to "/nix/store/yq03c2ny43mc24j7dq5riznzb09ddhpq-bash-4.4-p12/bin/sh -"
/nix/store/j45p7ifxr64s38zmrdv1icx7fs2b9y14-figlet-2.2.5/bin/showfigfonts: interpreter directive changed from "/bin/sh -" to "/nix/store/yq03c2ny43mc24j7dq5riznzb09ddhpq-bash-4.4-p12/bin/sh -"
checking for references to /tmp/nix-build-figlet-2.2.5.drv-0 in /nix/store/j45p7ifxr64s38zmrdv1icx7fs2b9y14-figlet-2.2.5...
/nix/store/j45p7ifxr64s38zmrdv1icx7fs2b9y14-figlet-2.2.5