From e87d4575643ee19c16242132167cf6dfa985dcce Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dani=C3=ABl=20de=20Kok?= <me@danieldk.eu>
Date: Thu, 3 Dec 2020 12:44:12 +0100
Subject: [PATCH] buildRustCrate: set NUM_JOBS to NIX_BUILD_CORES

Bofore this change, NUM_JOBS was set to 1. Some crates for building
C/C++ code (e.g. the cc and cmake crates), rely on this variable to
set the number of jobs. As a consequence, we were compiling embedded
libraries serially. Change this to NIX_BUILD_CORES to permit parallel
builds.

Prior discussion:

https://github.com/NixOS/nixpkgs/pull/50452#issuecomment-439407547
---
 pkgs/build-support/rust/build-rust-crate/configure-crate.nix | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pkgs/build-support/rust/build-rust-crate/configure-crate.nix b/pkgs/build-support/rust/build-rust-crate/configure-crate.nix
index 5ada40b3b9b..d1010ac1adb 100644
--- a/pkgs/build-support/rust/build-rust-crate/configure-crate.nix
+++ b/pkgs/build-support/rust/build-rust-crate/configure-crate.nix
@@ -144,7 +144,7 @@ in ''
   export CARGO_PKG_VERSION_PATCH=${lib.elemAt version 2}
   export CARGO_PKG_VERSION_PRE="${versionPre}"
   export CARGO_PKG_HOMEPAGE="${crateHomepage}"
-  export NUM_JOBS=1
+  export NUM_JOBS=$NIX_BUILD_CORES
   export RUSTC="rustc"
   export RUSTDOC="rustdoc"