mk: Switch rustbuild to the default build system

This commit switches the default build system for Rust from the makefiles to
rustbuild. The rustbuild build system has been in development for almost a year
now and has become quite mature over time. This commit is an implementation of
the proposal on [internals] which slates deletion of the makefiles on
2016-01-02.

[internals]: https://internals.rust-lang.org/t/proposal-for-promoting-rustbuild-to-official-status/4368

This commit also updates various documentation in `README.md`,
`CONTRIBUTING.md`, `src/bootstrap/README.md`, and throughout the source code of
rustbuild itself.

Closes #37858

1 files changed, 11 insertions, 5 deletions

diff --git a/src/liballoc_jemalloc/build.rs b/src/liballoc_jemalloc/build.rs
index 50149dfd65f..fc849e7a50c 100644
--- a/src/liballoc_jemalloc/build.rs
+++ b/src/liballoc_jemalloc/build.rs
@@ -151,11 +151,17 @@ fn main() {
     cmd.arg(format!("--build={}", build_helper::gnu_target(&host)));
 
     run(&mut cmd);
-    run(Command::new("make")
-        .current_dir(&build_dir)
-        .arg("build_lib_static")
-        .arg("-j")
-        .arg(env::var("NUM_JOBS").expect("NUM_JOBS was not set")));
+    let mut make = Command::new("make");
+    make.current_dir(&build_dir)
+        .arg("build_lib_static");
+
+    // mingw make seems... buggy? unclear...
+    if !host.contains("windows") {
+        make.arg("-j")
+            .arg(env::var("NUM_JOBS").expect("NUM_JOBS was not set"));
+    }
+
+    run(&mut make);
 
     if target.contains("windows") {
         println!("cargo:rustc-link-lib=static=jemalloc");