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: ../libmisc/libmisc.a(mlog.o):/build/libipfix_110209/libmisc/misc.h:111: multiple definition of
`ht_globals'; collector.o:/build/libipfix_110209/collector/../libmisc/misc.h:111: first defined here
