Fix "looking for rustc at …" message for stable when already bootstra…

…pped

Also always download from static-rust-lang-org.s3.amazonaws.com instead
of static.rust-lang.org. They host the same content, but the latter goes
through a CDN and has a TLS certificate that failed to verify and some
Python versions:

#3582
#3971

python/servo/bootstrap_commands.py

@@ -138,12 +138,7 @@ def bootstrap_rustc(self, force=False, target=[], stable=False):
         self.set_use_stable_rust(stable)
         version = self.rust_version()
         rust_path = self.rust_path()
-        if stable:
-            rust_dir = path.join(
-                self.context.sharedir, "rust", version, rust_path)
-        else:
-            rust_dir = path.join(
-                self.context.sharedir, "rust", rust_path)
+        rust_dir = path.join(self.context.sharedir, "rust", rust_path)
         install_dir = path.join(self.context.sharedir, "rust", version)
 
         if not force and path.exists(path.join(rust_dir, "rustc", "bin", "rustc" + BIN_SUFFIX)):
@@ -160,9 +155,10 @@ def bootstrap_rustc(self, force=False, target=[], stable=False):
             # giving a directory name that will be the same as the tarball name (rustc is
             # in that directory).
             if stable:
-                rustc_url = "https://static.rust-lang.org/dist/%s.tar.gz" % rust_path
+                tarball = "rustc-%s-%s.tar.gz" % (version, host_triple())
             else:
-                rustc_url = "https://static-rust-lang-org.s3.amazonaws.com/dist/%s.tar.gz" % rust_path
+                tarball = "%s/rustc-nightly-%s.tar.gz" % (version, host_triple())
+            rustc_url = "https://static-rust-lang-org.s3.amazonaws.com/dist/" + tarball
             tgz_file = rust_dir + '-rustc.tar.gz'
 
             download_file("Rust compiler", rustc_url, tgz_file)

python/servo/command_base.py

@@ -218,10 +218,11 @@ def use_stable_rust(self):
         return self._use_stable_rust
 
     def rust_path(self):
+        version = self.rust_version()
         if self._use_stable_rust:
-            return "rustc-%s-%s" % (self.rust_version(), host_triple())
+            return "%s/rustc-%s-%s" % (version, version, host_triple())
         else:
-            return "%s/rustc-nightly-%s" % (self.rust_version(), host_triple())
+            return "%s/rustc-nightly-%s" % (version, host_triple())
 
     def rust_version(self):
         if self._rust_version is None or self._use_stable_rust != self._rust_version_is_stable: