Auto merge of #4275 - alexcrichton:revert-makeflags, r=alexcrichton

Don't set MAKEFLAGS for build scripts

Closes #4156
Closes rust-lang/rust#42635

Author: bors

Cargo.lock

@@ -31,7 +31,7 @@ git2 = "0.6"
 git2-curl = "0.7"
 glob = "0.2"
 hex = "0.2"
-jobserver = "0.1.4"
+jobserver = "0.1.6"
 libc = "0.2"
 libgit2-sys = "0.6"
 log = "0.3"

Cargo.toml

@@ -61,6 +61,7 @@ fn _process(t: &OsStr) -> cargo::util::ProcessBuilder {
      .env_remove("EMAIL")
      .env_remove("MFLAGS")
      .env_remove("MAKEFLAGS")
+     .env_remove("CARGO_MAKEFLAGS")
      .env_remove("GIT_AUTHOR_NAME")
      .env_remove("GIT_AUTHOR_EMAIL")
      .env_remove("GIT_COMMITTER_NAME")

tests/cargotest/lib.rs

@@ -23,7 +23,7 @@ fn jobserver_exists() {
             use std::env;
 
             fn main() {
-                let var = env::var("MAKEFLAGS").unwrap();
+                let var = env::var("CARGO_MAKEFLAGS").unwrap();
                 let arg = var.split(' ')
                              .find(|p| p.starts_with("--jobserver"))
                              .unwrap();