fix(protocan): исправь вызов MSVC из host builder

c/protocan-transport/tools/build_host.py

@@ -51,9 +51,11 @@ def _build_msvc(output: Path, build_dir: Path) -> None:
     command = (
         f'call "{vcvars}" && cl /nologo /W4 /std:c11 '
         f'/DPCAN_ABI_BUILD_DLL /I"{INCLUDE}" /LD {quoted_sources} '
-        f'/Fe:"{output}"'
+        f'/Fe"{output}"'
     )
-    subprocess.run(["cmd.exe", "/d", "/c", command], cwd=build_dir, check=True)
+    # shell=True is intentional on Windows: ``call`` must run the batch file
+    # in the same cmd.exe process that subsequently launches cl.exe.
+    subprocess.run(command, cwd=build_dir, check=True, shell=True)
 
 
 def _build_cc(output: Path, build_dir: Path) -> None: