fix: exclude some build backends from python build backend lint/hint

conda_smithy/linter/hints.py

@@ -181,6 +181,13 @@ def hint_check_spdx(about_section, hints):
 
 
 def hint_pip_no_build_backend(host_or_build_section, package_name, hints):
+    # we do NOT exclude all build backends since some of them
+    # need another backend to bootstrap
+    # the list below are the ones that self-bootstrap without
+    # another build backend
+    if package_name in ["pdm-backend", "setuptools"]:
+        return
+
     if host_or_build_section and any(
         req.split(" ")[0] == "pip" for req in host_or_build_section
     ):

news/2046-pip-hint-exclude.rst

@@ -0,0 +1,23 @@
+**Added:**
+
+* <news item>
+
+**Changed:**
+
+* <news item>
+
+**Deprecated:**
+
+* <news item>
+
+**Removed:**
+
+* <news item>
+
+**Fixed:**
+
+* Fixed error where some python build backends were flagged as not having a backend. (#2046)
+
+**Security:**
+
+* <news item>