build: create group features for target systems

This allows a user to create builds with or without the Unix-specific
utilities. Right now the Makefile handles this, but this is needed to
migrate away from make.

To build Unix-specific utilities (default):

cargo build
(or)
cargo build --features unix --no-default-features

To build without the Unix-specific utilities:

cargo build --features generic --no-default-features

Cargo.toml

@@ -4,21 +4,39 @@ version = "0.0.1"
 authors = []
 build = "build.rs"
 
-
 [features]
-default = ["all"]
-all = [
+unix = [
+  "chroot",
+  "du",
+  "groups",
+  "hostid",
+  "hostname",
+  "id",
+  "kill",
+  "logname",
+  "mkfifo",
+  "mv",
+  "nice",
+  "nohup",
+  "stdbuf",
+  "timeout",
+  "touch",
+  "tty",
+  "uname",
+  "unlink",
+  "uptime",
+  "users",
+]
+generic = [
   "base64",
   "basename",
   "cat",
   "chmod",
-    "chroot",
   "cksum",
   "comm",
   "cp",
   "cut",
   "dirname",
-    "du",
   "echo",
   "env",
   "expand",
@@ -27,22 +45,12 @@ all = [
   "false",
   "fmt",
   "fold",
-    "groups",
   "hashsum",
   "head",
-    "hostid",
-    "hostname",
-    "id",
-    "kill",
   "link",
   "ln",
-    "logname",
   "mkdir",
-    "mkfifo",
-    "mv",
-    "nice",
   "nl",
-    "nohup",
   "nproc",
   "od",
   "paste",
@@ -59,30 +67,23 @@ all = [
   "sleep",
   "sort",
   "split",
-    "stdbuf",
   "sum",
   "sync",
   "tac",
   "tail",
   "tee",
   "test",
-    "timeout",
-    "touch",
   "tr",
   "true",
   "truncate",
   "tsort",
-    "tty",
-    "uname",
   "unexpand",
   "uniq",
-    "unlink",
-    "uptime",
-    "users",
   "wc",
   "whoami",
   "yes",
 ]
+default = ["generic", "unix"]
 
 [dependencies]
 uucore   = { path="src/uucore" }
@@ -178,4 +179,3 @@ tempdir="*"
 [[bin]]
 name="uutils"
 path="src/uutils/uutils.rs"
-

build.rs

@@ -12,8 +12,7 @@ pub fn main() {
         if val == "1" && key.starts_with(feature_prefix) {
             let krate = key[feature_prefix.len()..].to_lowercase();
             match krate.as_ref() {
-            "default" => continue,
-            "all" => continue,
+            "default" | "unix" | "generic" => continue,
             _ => {},
             }
             crates.push(krate.to_string());