Use Cargo's target directory sharing.

This speeds up `./mach build --dev` followed by `./mach build-cef` by a
large amount, and also speeds up other build combos found in our CI.

python/servo/build_commands.py

@@ -147,7 +147,7 @@ class MachCommands(CommandBase):
         opts = params or []
         features = []
 
-        base_path = path.join("components", "servo", "target")
+        base_path = self.get_target_dir()
         release_path = path.join(base_path, "release", "servo")
         dev_path = path.join(base_path, "debug", "servo")
 

python/servo/command_base.py

@@ -130,8 +130,14 @@ class CommandBase(object):
             self._cargo_build_id = open(filename).read().strip()
         return self._cargo_build_id
 
+    def get_target_dir(self):
+        if "CARGO_TARGET_DIR" in os.environ:
+            return os.environ["CARGO_TARGET_DIR"]
+        else:
+            return path.join(self.context.topdir, "target")
+
     def get_binary_path(self, release, dev):
-        base_path = path.join("components", "servo", "target")
+        base_path = self.get_target_dir()
         release_path = path.join(base_path, "release", "servo")
         dev_path = path.join(base_path, "debug", "servo")
 
@@ -199,6 +205,9 @@ class CommandBase(object):
         if "CARGO_HOME" not in env:
             env["CARGO_HOME"] = self.config["tools"]["cargo-home-dir"]
 
+        if "CARGO_TARGET_DIR" not in env:
+            env["CARGO_TARGET_DIR"] = path.join(self.context.topdir, "target")
+
         if extra_lib:
             if sys.platform == "darwin":
                 env["DYLD_LIBRARY_PATH"] = "%s%s%s" % \

python/servo/post_build_commands.py

@@ -137,8 +137,7 @@ class MachCommands(CommandBase):
         if not path.exists(path.join(self.config["tools"]["rust-root"], "doc")):
             Registrar.dispatch("bootstrap-rust-docs", context=self.context)
         rust_docs = path.join(self.config["tools"]["rust-root"], "doc")
-        docs = path.join(
-            self.context.topdir, "components", "servo", "target", "doc")
+        docs = path.join(self.get_target_dir(), "doc")
         if not path.exists(docs):
             os.makedirs(docs)
 
@@ -167,4 +166,4 @@ class MachCommands(CommandBase):
         self.doc([])
         import webbrowser
         webbrowser.open("file://" + path.abspath(path.join(
-            self.servo_crate(), "target", "doc", "servo", "index.html")))
+            self.get_target_dir(), "doc", "servo", "index.html")))

python/servo/testing_commands.py

@@ -47,12 +47,11 @@ class MachCommands(CommandBase):
 
     def find_test(self, prefix):
         target_contents = os.listdir(path.join(
-            self.context.topdir, "components", "servo", "target", "debug"))
+            self.get_target_dir(), "debug"))
         for filename in target_contents:
             if filename.startswith(prefix + "-"):
                 filepath = path.join(
-                    self.context.topdir, "components", "servo",
-                    "target", "debug", filename)
+                    self.get_target_dir(), "debug", filename)
 
                 if path.isfile(filepath) and os.access(filepath, os.X_OK):
                     return filepath

python/tidy.py

@@ -36,8 +36,7 @@ ignored_files = [
     # Generated and upstream code combined with our own. Could use cleanup
     "components/script/dom/bindings/codegen/*",
     "components/style/properties/mod.rs",
-    "components/servo/target/*",
-    "ports/gonk/target/*",
+    "target/*",
     "ports/gonk/src/native_window_glue.cpp",
     "ports/cef/*",