Update mozangle, cc, and cmake

This also moves some environment variable configuration to the shared
`build_env()` method, because previously clang was only being chosen for
running `./mach build` and not `./mach test-unit` which was leading to
rebuilds and thus build failures when running `test-unit`. I guess the
cmake crate does not expect the compiler to change between subsequent
runs.

python/servo/build_commands.py

@@ -118,7 +118,6 @@ class MachCommands(CommandBase):
         self.ensure_clobbered()
 
         build_start = time()
-        env["CARGO_TARGET_DIR"] = target_path
 
         host = servo.platform.host_triple()
         target_triple = self.cross_compile_target or servo.platform.host_triple()
@@ -401,10 +400,6 @@ class MachCommands(CommandBase):
             for key in env:
                 print((key, env[key]))
 
-        if sys.platform != "win32":
-            env.setdefault("CC", "clang")
-            env.setdefault("CXX", "clang++")
-
         status = self.run_cargo_build_like_command(
             "build", opts, env=env, verbose=verbose,
             libsimpleservo=libsimpleservo, **kwargs

python/servo/command_base.py

@@ -496,7 +496,7 @@ class CommandBase(object):
             'vcdir': vcinstalldir,
         }
 
-    def build_env(self, is_build=False, test_unit=False):
+    def build_env(self, is_build=False):
         """Return an extended environment dictionary."""
         env = os.environ.copy()
 
@@ -557,6 +557,10 @@ class CommandBase(object):
             # Always build harfbuzz from source
             env["HARFBUZZ_SYS_NO_PKG_CONFIG"] = "true"
 
+        if sys.platform != "win32":
+            env.setdefault("CC", "clang")
+            env.setdefault("CXX", "clang++")
+
         if extra_path:
             util.append_paths_to_env(env, "PATH", extra_path)
 
@@ -597,11 +601,6 @@ class CommandBase(object):
         if "ANDROID_TOOLCHAIN" in env:
             env["NDK_STANDALONE"] = env["ANDROID_TOOLCHAIN"]
 
-        if test_unit and "msvc" in servo.platform.host_triple():
-            # on MSVC, we need some DLLs in the path. They were copied
-            # in to the servo.exe build dir, so just point PATH to that.
-            util.prepend_paths_to_env(env, "PATH", path.dirname(self.get_binary_path(False, False)))
-
         if self.config["build"]["rustflags"]:
             env['RUSTFLAGS'] = env.get('RUSTFLAGS', "") + " " + self.config["build"]["rustflags"]
 
@@ -619,6 +618,7 @@ class CommandBase(object):
             env['RUSTFLAGS'] = env.get('RUSTFLAGS', "") + " -C target-feature=+neon"
 
         env['RUSTFLAGS'] = env.get('RUSTFLAGS', "") + " -W unused-extern-crates"
+        env["CARGO_TARGET_DIR"] = servo.util.get_target_dir()
 
         git_info = []
         if os.path.isdir('.git') and is_build:

python/servo/testing_commands.py

@@ -31,6 +31,8 @@ from mach.decorators import (
     CommandProvider,
     Command,
 )
+
+import servo.util
 import tidy
 
 from servo.command_base import (
@@ -260,10 +262,20 @@ class MachCommands(CommandBase):
         if nocapture:
             args += ["--", "--nocapture"]
 
+        # We are setting is_build here to true, because running `cargo test` can trigger builds.
+        env = self.build_env(is_build=True)
+
+        # on MSVC, we need some DLLs in the path. They were copied
+        # in to the servo.exe build dir, so just point PATH to that.
+        # TODO(mrobinson): This should be removed entirely.
+        if "msvc" in servo.platform.host_triple():
+            servo.util.prepend_paths_to_env(
+                env, "PATH", path.dirname(self.get_binary_path(False, False)))
+
         return self.run_cargo_build_like_command(
             "bench" if bench else "test",
             args,
-            env=self.build_env(test_unit=True),
+            env=env,
             with_layout_2020=with_layout_2020,
             **kwargs)