1. Call `nix-build` with `--no-out-link` to avoid cluttering the source dir.
2. Re-add `patchShebangs`, since `buildCommand` doesn't imply a patch phase. (It was my fault to remove this in the first place, sorry!)
This should avoid the 28 lines of unnecessary spam about fetching stdenv
and bash:
````
=== Building pull request #28261
these paths will be fetched (0.51 MiB download, 2.50 MiB unpacked):
/nix/store/2pm24nzym7z11nddnf6vmqhsqmzx9h3g-bash-4.4-p12-dev
/nix/store/3n6g5nmyn63gsgjc7z03rsd88s2q7b7i-stdenv
/nix/store/7mpcc6x6b3db595rsqr1qjckpaj1dym8-bash-4.4-p12-info
/nix/store/d9hb8f6j2syq08hw97qajdcdkl9lwg9n-bash-4.4-p12-doc
fetching path ‘/nix/store/d9hb8f6j2syq08hw97qajdcdkl9lwg9n-bash-4.4-p12-doc’...
*** Downloading ‘https://cache.nixos.org/nar/013kcshsm2hzpngmrf4izq3ag8s9avrkhz5z8l8mgnxay1lxlz99.nar.xz’ to ‘/nix/store/d9hb8f6j2syq08hw97qajdcdkl9lwg9n-bash-4.4-p12-doc’...
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 357k 100 357k 0 0 3342k 0 --:--:-- --:--:-- --:--:-- 3408k
fetching path ‘/nix/store/2pm24nzym7z11nddnf6vmqhsqmzx9h3g-bash-4.4-p12-dev’...
*** Downloading ‘https://cache.nixos.org/nar/1225myjpymp5bv0x5zl08dmdz786jf86fshc2dwa3zgxasrppcfi.nar.xz’ to ‘/nix/store/2pm24nzym7z11nddnf6vmqhsqmzx9h3g-bash-4.4-p12-dev’...
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 54312 100 54312 0 0 231k 0 --:--:-- --:--:-- --:--:-- 232k
fetching path ‘/nix/store/7mpcc6x6b3db595rsqr1qjckpaj1dym8-bash-4.4-p12-info’...
*** Downloading ‘https://cache.nixos.org/nar/04dzl4jlhxhisiby9lyw2k6q2w5ns3xy1h6gfdc14qn649lshy2f.nar.xz’ to ‘/nix/store/7mpcc6x6b3db595rsqr1qjckpaj1dym8-bash-4.4-p12-info’...
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 107k 100 107k 0 0 1179k 0 --:--:-- --:--:-- --:--:-- 1198k
fetching path ‘/nix/store/3n6g5nmyn63gsgjc7z03rsd88s2q7b7i-stdenv’...
*** Downloading ‘https://cache.nixos.org/nar/013xg2cnv9wf3fkhcl3b3b6iihqnwhy65m6ijb6ynwavy584w2xi.nar.xz’ to ‘/nix/store/3n6g5nmyn63gsgjc7z03rsd88s2q7b7i-stdenv’...
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 8640 100 8640 0 0 143k 0 --:--:-- --:--:-- --:--:-- 148k
=== Reviewing PR 28261 : busybox: 1.26.2 -> 1.27.1, fix bootstrap
````
(From https://travis-ci.org/NixOS/nixpkgs/jobs/264390932)
"Builder called die: Cannot wrap
/nix/store/XXX-munin-available-plugins/plugin.sh because it is not an
executable file"
[Bjørn: Keep DRY, quote "$file".]
