get the env var into the container

Author: chadrik

.github/workflows/wheel.yml

@@ -150,7 +150,7 @@ jobs:
       - name: Build wheels
         uses: pypa/cibuildwheel@d4a2945fcc8d13f20a1b99d461b8e844d5fc6e23 # v2.21.1
         env:
-          OIIO_VALIDATE_STUBS: "true"
+          CIBW_ENVIRONMENT: OIIO_VALIDATE_STUBS="true"
           CIBW_BUILD: ${{ matrix.python }}
           CIBW_ARCHS: ${{ matrix.arch }}
           CIBW_MANYLINUX_X86_64_IMAGE: ${{ matrix.manylinux }}