[3.11] gh-94801: Use custom flags to check for headers and libs (GH-94802) (GH-94881)

Co-authored-by: Christian Heimes <[email protected]>

Author: tiran

Misc/NEWS.d/next/Build/2022-07-13-10-13-10.gh-issue-94801.3xUB24.rst

@@ -0,0 +1,2 @@
+``configure`` now uses custom flags like ``ZLIB_CFLAGS`` and ``ZLIB_LIBS``
+when searching for headers and libraries.