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: daemonize.o:/build/ucarp-1.5.2/src/ip_carp.h:73: multiple definition of
`__packed'; ucarp.o:/build/ucarp-1.5.2/src/ip_carp.h:73: first defined here
