Fix shell syntax in build_wheel

Follow up to python#11872
The cross repo split makes this a bit of a pain to test.

Author: hauntsaninja

misc/build_wheel.py

@@ -75,9 +75,12 @@ def create_environ(python_version: str) -> Dict[str, str]:
 
     # lxml doesn't have a wheel for Python 3.10 on the manylinux image we use.
     # lxml has historically been slow to support new Pythons as well.
-    env['CIBW_BEFORE_TEST'] = (
-        'pip install -r <(grep -v lxml {project}/mypy/test-requirements.txt)'
-    )
+    env['CIBW_BEFORE_TEST'] = """
+      (
+      grep -v lxml {project}/mypy/test-requirements.txt > /tmp/requirements.txt
+      && pip install -r /tmp/requirements.txt
+      )
+    """
 
     # pytest looks for configuration files in the parent directories of where the tests live.
     # since we are trying to run the tests from their installed location, we copy those into