Apply the correct fix with PIP_CONSTRAINTS

Author: ggeorgakoudis

pyproject.toml

@@ -49,11 +49,14 @@ archs = ["native"]
 # Pass LLVM_VERSION from the host environment to cibuildwheel.
 environment-pass = ["LLVM_VERSION"]
 # We use miniconda3 to get the clang/llvm toolchain on Linux.
-before-build = ["rm -rf build dist src/*.egg-info"]
+before-build = [
+    "rm -rf build dist src/*.egg-info",
+    # llvmlite needs setuptools < 82 to build from source, if needed. Create a
+    # constraints file used by PIP_CONSTRAINT to enforce this in isolated
+    # builds.
+    "echo 'setuptools<82' > /tmp/constraints.txt",
+]
 skip = ["*-musllinux_*", "cp38-*"]
-# llvmlite needs setuptools < 82, and we may need to build from source, so we
-# ensure that setuptools is in the correct version range.
-test-requires = ["setuptools>=75.3,<82"]
 test-command = [
     # Run host OpenMP tests.
     "TEST_DEVICES=0 RUN_TARGET=0 python -m numba.runtests -v -- numba.openmp.tests.test_openmp",
@@ -64,6 +67,8 @@ test-command = [
 [tool.cibuildwheel.environment]
 USE_CXX11_ABI = "1"
 PIP_NO_INPUT = "1"
+# Enforce setuptools version even in isolated builds for llvmlite compatibility.
+PIP_CONSTRAINT = "/tmp/constraints.txt"
 
 [tool.cibuildwheel.linux]
 before-all = [