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 -fno-common toolchains like upstream gcc-10
or clang-11+ fail to build simh as:
$ nix build --impure --expr 'with import ~/nm {}; simh.override { stdenv = clang13Stdenv; }'
...
ld: /build/pdp11_io-0c74f0.o:(.bss+0x10c00):
multiple definition of `uc15_memsize'; /build/pdp11_cis-17339e.o:(.bss+0x118): first defined here
ld: /build/pdp11_io_lib-296a06.o:(.bss+0x8000):
multiple definition of `uc15_memsize'; /build/pdp11_cis-17339e.o:(.bss+0x118): first defined here
