x.py: allow configuring the build directory

config.toml.example

@@ -131,6 +131,10 @@
 # for each target triple.
 #target = ["x86_64-unknown-linux-gnu"] # defaults to just the build triple
 
+# Use this directory to store build artifacts.
+# You can use "$ROOT" to indicate the root of the git repository.
+#build-dir = "build"
+
 # Instead of downloading the src/stage0.txt version of Cargo specified, use
 # this Cargo binary instead to build all Rust code
 #cargo = "/path/to/bin/cargo"

src/bootstrap/bootstrap.py

@@ -332,7 +332,7 @@ def __init__(self):
  self.rustc_channel = ''
  self.rustfmt_channel = ''
  self.build = ''
- self.build_dir = os.path.join(os.getcwd(), "build")
+ self.build_dir = ''
  self.clean = False
  self.config_toml = ''
  self.rust_root = ''
@@ -891,7 +891,11 @@ def bootstrap(help_triggered):
  build.clean = args.clean
 
  try:
- with open(args.config or 'config.toml') as config:
+ toml_path = args.config or 'config.toml'
+ if not os.path.exists(toml_path):
+ toml_path = os.path.join(build.rust_root, toml_path)
+
+ with open(toml_path) as config:
  build.config_toml = config.read()
  except (OSError, IOError):
  pass
@@ -906,6 +910,9 @@ def bootstrap(help_triggered):
 
  build.check_vendored_status()
 
+ build_dir = build.get_toml('build-dir', 'build') or 'build'
+ build.build_dir = os.path.abspath(build_dir.replace("$ROOT", build.rust_root))
+
  data = stage0_data(build.rust_root)
  build.date = data['date']
  build.rustc_channel = data['rustc']

src/bootstrap/config.rs

@@ -212,6 +212,8 @@ struct Build {
  host: Vec<String>,
  #[serde(default)]
  target: Vec<String>,
+ // This is ignored, the rust code always gets the build directory from the `BUILD_DIR` env variable
+ build_dir: Option<String>,
  cargo: Option<String>,
  rustc: Option<String>,
  rustfmt: Option<String>, /* allow bootstrap.py to use rustfmt key */