I am uploading a NMU with the attached debdiff to DELAYED/10 to fix this.
diff -Nru pillow-9.4.0/debian/changelog pillow-9.4.0/debian/changelog
--- pillow-9.4.0/debian/changelog 2023-01-03 10:06:46.000000000 +0100
+++ pillow-9.4.0/debian/changelog 2023-01-16 16:29:25.000000000 +0100
@@ -1,3 +1,10 @@
+pillow (9.4.0-1.1) unstable; urgency=medium
+
+ * Non-maintainer upload.
+ * Handle more than one directory returned by pkg-config (Closes: #1028904).
+
+ -- Bastian Germann <b...@debian.org> Mon, 16 Jan 2023 16:29:25 +0100
+
pillow (9.4.0-1) unstable; urgency=medium
* New upstream version.
diff -Nru pillow-9.4.0/debian/patches/pkg-config-multiarch.diff
pillow-9.4.0/debian/patches/pkg-config-multiarch.diff
--- pillow-9.4.0/debian/patches/pkg-config-multiarch.diff 1970-01-01
01:00:00.000000000 +0100
+++ pillow-9.4.0/debian/patches/pkg-config-multiarch.diff 2023-01-16
16:20:19.000000000 +0100
@@ -0,0 +1,63 @@
+From 04cf5e2cfc5dc1676efd9f5c8d605ddfccb0f9ee Mon Sep 17 00:00:00 2001
+From: Bas Couwenberg <sebas...@xs4all.nl>
+Date: Sat, 14 Jan 2023 19:09:43 +0100
+Subject: Handle more than one directory returned by pkg-config.
+
+tiff (4.5.0-1) in Debian results in two include directories being returned:
+```
+-I/usr/include/x86_64-linux-gnu -I/usr/include
+```
+---
+ setup.py | 24 +++++++++++++++---------
+ 1 file changed, 15 insertions(+), 9 deletions(-)
+
+diff --git a/setup.py b/setup.py
+index 243365681..b4ebbb9c2 100755
+--- a/setup.py
++++ b/setup.py
+@@ -263,18 +263,20 @@ def _pkg_config(name):
+ if not DEBUG:
+ command_libs.append("--silence-errors")
+ command_cflags.append("--silence-errors")
+- libs = (
++ libs = re.split(
++ r"\s*-L",
+ subprocess.check_output(command_libs, stderr=stderr)
+ .decode("utf8")
+- .strip()
+- .replace("-L", "")
++ .strip(),
+ )
+- cflags = (
+- subprocess.check_output(command_cflags)
++ libs.remove("")
++ cflags = re.split(
++ r"\s*-I",
++ subprocess.check_output(command_cflags, stderr=stderr)
+ .decode("utf8")
+- .strip()
+- .replace("-I", "")
++ .strip(),
+ )
++ cflags.remove("")
+ return libs, cflags
+ except Exception:
+ pass
+@@ -473,8 +475,12 @@ class pil_build_ext(build_ext):
+ else:
+ lib_root = include_root = root
+
+- _add_directory(library_dirs, lib_root)
+- _add_directory(include_dirs, include_root)
++ if lib_root is not None:
++ for lib_dir in lib_root:
++ _add_directory(library_dirs, lib_dir)
++ if include_root is not None:
++ for include_dir in include_root:
++ _add_directory(include_dirs, include_dir)
+
+ # respect CFLAGS/CPPFLAGS/LDFLAGS
+ for k in ("CFLAGS", "CPPFLAGS", "LDFLAGS"):
+--
+2.30.2
+
diff -Nru pillow-9.4.0/debian/patches/series pillow-9.4.0/debian/patches/series
--- pillow-9.4.0/debian/patches/series 2022-10-21 17:53:14.000000000 +0200
+++ pillow-9.4.0/debian/patches/series 2023-01-16 16:27:58.000000000 +0100
@@ -4,3 +4,4 @@
no-sphinx-removed-in.diff
no-sphinx-opengraph.diff
no-sphinx-furo.diff
+pkg-config-multiarch.diff
