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
Workaround build failure on -fno-common toolchains like upstream
gcc-10. Otherwise build fails as:
ld: inout.o:/build/chemtool-1.6.14/ct1.h:279: multiple definition of
`outtype'; draw.o:/build/chemtool-1.6.14/ct1.h:279: first defined here
