`multiPaths` is defined via invalid operation on `null` value for
non-multilib environments. Noticed on `notesnook` evan failure as:
nix-repl> notesnook.fhsenv.multiPaths
253| passthru = {
254| inherit args baseTargetPaths targetPaths baseMultiPaths multiPaths ldconfig;
| ^
255| };
error: attempt to call something which is not a function but null
The change makes `multiPaths` a private variable.
It's useful to be able to introspect all packages which are available
in the fhsenv. I've renamed basePkgs and baseMultiPkgs to be
consistent with the naming scheme used for the bits that were
previously public — names ending in "Pkgs" are for functions, and
names ending in "Paths" are the results of those functions.
Before the change the following command did not work:
$ nix develop -i --impure --expr 'with import <nixpkgs> { system = "i686-linux"; }; (buildFHSUserEnv { name = "t"; targetPkgs = ps: with ps; [ libmpc stdenv.cc ]; }).env'
$ ld -lmpc -o a
ld: cannot find -lmpc: No such file or directory
It is expected to work as `NIX_LDFLAGS` does contain valid values:
$ echo $NIX_LDFLAGS
-L/usr/lib -L/usr/lib32
Note that for `gcc` it does work:
$ printf "int main(){}" | gcc -x c - -lmpc -o a
It happens because `HOST` role is enabled for `cc`:
$ echo $NIX_CC_WRAPPER_TARGET_HOST_i686_unknown_linux_gnu
1
But not for `BINTOOLS`:
$ echo $NIX_BINTOOLS_WRAPPER_TARGET_HOST_i686_unknown_linux_gnu
<empty>
The change adds BINTOOLS role and fixes linking:
$ nix develop -i --impure --expr 'with import ~/nm { system = "i686-linux"; }; (buildFHSUserEnv { name = "t"; targetPkgs = ps: with ps; [ libmpc stdenv.cc ]; }).env'
$ printf "int main(){}" | gcc -x c - -lmpc -o a
$ ld -lmpc -o a
ld: warning: cannot find entry symbol _start; not setting start address
Most FHSEnv-wrapped packages in Nixpkgs wrap a x86_64-linux binary; making
multiArch unnecessary bloat closure size. Saves about 1G in anki-bin.
This makes multiArch FHSEnvs the exception rather than the rule.
