Remove run shell from build scripts runner (#355)

cargo/cargo_build_script.bzl

@@ -71,18 +71,18 @@ def _cargo_build_script_run(ctx, script):
     # available to the current crate build script.
     # See https://doc.rust-lang.org/cargo/reference/build-scripts.html#-sys-packages
     # for details.
-    cmd = ""
+    args = ctx.actions.args()
+    args.add_all([script.path, crate_name, out_dir.path, env_out.path, flags_out.path, link_flags.path, dep_env_out.path])
     dep_env_files = []
     for dep in ctx.attr.deps:
         if DepInfo in dep and dep[DepInfo].dep_env:
             dep_env_file = dep[DepInfo].dep_env
-            cmd += "export $(cat %s); " % dep_env_file.path
+            args.add(dep_env_file.path)
             dep_env_files.append(dep_env_file)
-    cmd += "$@"
 
-    ctx.actions.run_shell(
-        command = cmd,
-        arguments = [ctx.executable._cargo_build_script_runner.path, script.path, crate_name, out_dir.path, env_out.path, flags_out.path, link_flags.path, dep_env_out.path],
+    ctx.actions.run(
+        executable = ctx.executable._cargo_build_script_runner,
+        arguments = [args],
         outputs = [out_dir, env_out, flags_out, link_flags, dep_env_out],
         tools = tools,
         inputs = dep_env_files,
@@ -131,7 +131,7 @@ _build_script_run = rule(
     ],
 )
 
-def cargo_build_script(name, crate_name="", crate_features=[], deps=[], **kwargs):
+def cargo_build_script(name, crate_name = "", crate_features = [], deps = [], **kwargs):
     """
     Compile and execute a rust build script to generate build attributes
 
@@ -184,7 +184,7 @@ def cargo_build_script(name, crate_name="", crate_features=[], deps=[], **kwargs
         name = name + "_script_",
         crate_features = crate_features,
         deps = deps,
-        **kwargs,
+        **kwargs
     )
     _build_script_run(
         name = name,

cargo/cargo_build_script_runner/bin.rs

@@ -19,7 +19,7 @@ extern crate cargo_build_script_output_parser;
 use cargo_build_script_output_parser::{BuildScriptOutput, CompileAndLinkFlags};
 use std::env;
 use std::ffi::OsString;
-use std::fs::{create_dir_all, write};
+use std::fs::{create_dir_all, read_to_string, write};
 use std::path::Path;
 use std::process::Command;
 
@@ -45,16 +45,34 @@ fn main() -> Result<(), String> {
 
             let mut command = Command::new(exec_root.join(&progname));
             command
-                .args(args)
                 .current_dir(manifest_dir.clone())
                 .env("OUT_DIR", out_dir_abs)
                 .env("CARGO_MANIFEST_DIR", manifest_dir)
                 .env("RUSTC", rustc)
                 .env("RUST_BACKTRACE", "full");
 
+            while let Some(dep_env_path) = args.next() {
+                if let Ok(contents) = read_to_string(dep_env_path) {
+                    for line in contents.split('\n') {
+                        let mut key_val = line.splitn(2, '=');
+                        match (key_val.next(), key_val.next()) {
+                            (Some(key), Some(value)) => {
+                                command.env(key, value);
+                            }
+                            _ => {
+                                return Err("error: Wrong environment file format, should not happen".to_owned())
+                            }
+                        }
+                    }
+                } else {
+                    return Err("error: Dependency environment file unreadable".to_owned())
+                }
+            }
+
             if let Some(cc_path) = env::var_os("CC") {
                 command.env("CC", absolutify(&exec_root, cc_path));
             }
+
             if let Some(ar_path) = env::var_os("AR") {
                 // The default OSX toolchain uses libtool as ar_executable not ar.
                 // This doesn't work when used as $AR, so simply don't set it - tools will probably fall back to