Merge pull request opencv#19522 from zchrissirhcz:3.4-fix-android-find-zlib-shared-since-ndk19

* fix find zlib.so instead of zlib.a when NDK >= 19

On Android platform, `libopencv_imgcodecs.a` is built, expected to
depend on `libz.so`. However, since Android NDK r19, NDK's `libz.a`
is found instead of `libz.so`, leading to link error
(not found libz.a) on machines without same NDK version & direcotry.

Since Android NDK-r19, toolchain pieces are installed to
`$NDK/toolchains/llvm/prebuilt/<host-tag>/...`, including `libz.so`.
Also installed to old paths (`<NDK>/platforms` and `<NDK>/sysroot`)
in NDK r19, r20, r21, but since NDK 22, old paths are removed.

- https://github.com/android/ndk/wiki/Changelog-r19
- https://github.com/android/ndk/wiki/Changelog-r22

With this commit, `libz.so` can be correctly found in NDK<19 and NDK>=19.

`ZLIB_LIBRARIES` is also simplified as `z`, by appending match (regex)
patterns for new toolchain installation directory's libz.so's paths.

* simplify libz.so match pattern for abbreviation

Author: zchrissirhcz

cmake/OpenCVFindLibsGrfmt.cmake

@@ -7,9 +7,17 @@ if(BUILD_ZLIB)
   ocv_clear_vars(ZLIB_FOUND)
 else()
   ocv_clear_internal_cache_vars(ZLIB_LIBRARY ZLIB_INCLUDE_DIR)
+  if(ANDROID)
+    set(_zlib_ORIG_CMAKE_FIND_LIBRARY_SUFFIXES ${CMAKE_FIND_LIBRARY_SUFFIXES})
+    set(CMAKE_FIND_LIBRARY_SUFFIXES .so)
+  endif()
   find_package(ZLIB "${MIN_VER_ZLIB}")
+  if(ANDROID)
+    set(CMAKE_FIND_LIBRARY_SUFFIXES ${_zlib_ORIG_CMAKE_FIND_LIBRARY_SUFFIXES})
+    unset(_zlib_ORIG_CMAKE_FIND_LIBRARY_SUFFIXES)
+  endif()
   if(ZLIB_FOUND AND ANDROID)
-    if(ZLIB_LIBRARIES MATCHES "/usr/(lib|lib32|lib64)/libz.so$")
+    if(ZLIB_LIBRARIES MATCHES "/usr/lib.*/libz.so$")
       set(ZLIB_LIBRARIES z)
     endif()
   endif()