Auto merge of #18145 - tigercosmos:master, r=larsbergstrom

fix windows build issue #18055

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With some reasons, the windows and VS environment do not set the `env("PLATFORM")` variable.
So, there's no need to check the variable, and set `os_type` equl to `pc-windows-msvc` as default. Then the script can get correct url to download `rustc`.

---
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- [ ] `./mach build -d` does not report any errors
- [ ] `./mach test-tidy` does not report any errors
- [ ] These changes fix #18055 (github issue number if applicable).

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- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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python/servo/util.py

@@ -37,11 +37,7 @@ def host_platform():
     elif os_type == "android":
         os_type = "linux-androideabi"
     elif os_type == "windows":
-        # If we are in a Visual Studio environment, use msvc
-        if os.getenv("PLATFORM") is not None:
-            os_type = "pc-windows-msvc"
-        else:
-            os_type = "unknown"
+        os_type = "pc-windows-msvc"
     elif os_type == "freebsd":
         os_type = "unknown-freebsd"
     else:
@@ -52,16 +48,7 @@ def host_platform():
 def host_triple():
     os_type = host_platform()
     cpu_type = platform.machine().lower()
-    if os_type.endswith("-msvc"):
-        # vcvars*.bat should set it properly
-        platform_env = os.environ.get("PLATFORM").upper()
-        if platform_env == "X86":
-            cpu_type = "i686"
-        elif platform_env == "X64":
-            cpu_type = "x86_64"
-        else:
-            cpu_type = "unknown"
-    elif cpu_type in ["i386", "i486", "i686", "i768", "x86"]:
+    if cpu_type in ["i386", "i486", "i686", "i768", "x86"]:
         cpu_type = "i686"
     elif cpu_type in ["x86_64", "x86-64", "x64", "amd64"]:
         cpu_type = "x86_64"