"sysconfig --generate-posix-vars" creates pybuilddir.txt and a platform-specific sysconfig data file like build/lib.linux-x86_64-3.11/_sysconfigdata__linux_x86_64-linux-gnu.py

When creating a cross-compile build of Python, sysconfig mixes data from the cross compile build and the host build. It creates a pybuilddir.txt and build/lib directory with correct values (e.g. wasm32-unknown-emscripten) but sysconfigdata file with name values from the host Python PYTHON_FOR_BUILD (e.g x86_64-unknown-linux-gnu). 

$ cat pybuilddir.txt 
build/lib.wasm32-unknown-emscripten-3.11

$ ls build/lib.wasm32-unknown-emscripten-3.11/_sysconfigdata*                           
build/lib.wasm32-unknown-emscripten-3.11/_sysconfigdata__linux_x86_64-linux-gnu.py

$ grep CC build/lib.wasm32-unknown-emscripten-3.11/_sysconfigdata__linux_x86_64-linux-gnu.py 
 'CC': 'gcc',

$ grep ^CC Makefile
CC=             emcc