The nixpkgs-unstable channel's programs.sqlite was used to identify
packages producing exactly one binary, and these automatically added
to their package definitions wherever possible.
with structuredAttrs lists will be bash arrays which cannot be exported
which will be a issue with some patches and some wrappers like cc-wrapper
this makes it clearer that NIX_CFLAGS_COMPILE must be a string as lists
in env cause a eval failure
Without the change the build fails on -fno-common toolchains like gcc-10 as:
$ nix build --impure --expr 'with import ./. {}; g15daemon.override { stdenv = clang13Stdenv; }'
ld: g15daemon.h:218: multiple definition of `lcdlist_mutex'; utility_funcs.o:g15daemon.h:218: first defined here
ld: g15daemon.h:203: multiple definition of `lcdnode_s'; utility_funcs.o:g15daemon.h:203: first defined here
