CMake: Introduce zlib find script to work around hardcoded iOS SDK

Xcode allows building a project targeting either the device or
simulator sysroot in one single build dir, but for the sysroot
switching to work there should be no linker or compiler flags
referencing absolute paths of a specific sysroot.

During CMake configuration of a project targeting iOS, all found
system libraries will be within one single sysroot, either the device
one or the simulator one, whichever one was passed to
CMAKE_OSX_SYSROOT. CMake will then generate the Xcode project
and pass those absolute paths, which makes sysroot switching within
Xcode not work.

To avoid that, the CMake documentation recommends passing linker and
framework flags of the form '-lfoo' and '-framework bar' instead of
absolute paths. Xcode then takes care of setting the correct framework
search path.

Zlib is one of the libraries found in the iOS sysroot and thus passed
as absolute path.
To avoid that, create a new FindWrapZLIB find script. The target it
creates will pass the absolute path to the library on non Apple
platforms and an -lz linker flag on Apple platforms (macOS and iOS).

To avoid issues with target global promotion when system PNG package
is found, ensure that a found ZLIB::ZLIB target is promoted to global
manually in src/gui/configure.cmake.

Pick-to: 6.1
Change-Id: I8bd8649be4f680a331ad51925f27cb9d13ac5e5f
Reviewed-by: Cristian Adam <cristian.adam@qt.io>

6 files changed, 6 insertions, 6 deletions

diff --git a/src/3rdparty/freetype/CMakeLists.txt b/src/3rdparty/freetype/CMakeLists.txt
index 13f2c434c0..6a9de38984 100644
--- a/src/3rdparty/freetype/CMakeLists.txt
+++ b/src/3rdparty/freetype/CMakeLists.txt
@@ -78,7 +78,7 @@ qt_internal_extend_target(BundledFreetype CONDITION QT_FEATURE_png
 
 qt_internal_extend_target(BundledFreetype CONDITION QT_FEATURE_system_zlib
     LIBRARIES
-        ZLIB::ZLIB
+        WrapZLIB::WrapZLIB
 )
 
 qt_internal_extend_target(BundledFreetype CONDITION NOT QT_FEATURE_system_zlib
diff --git a/src/3rdparty/libpng/CMakeLists.txt b/src/3rdparty/libpng/CMakeLists.txt
index e07272f7c6..637ebcf548 100644
--- a/src/3rdparty/libpng/CMakeLists.txt
+++ b/src/3rdparty/libpng/CMakeLists.txt
@@ -42,7 +42,7 @@ qt_set_symbol_visibility_hidden(BundledLibpng)
 
 qt_internal_extend_target(BundledLibpng CONDITION QT_FEATURE_system_zlib
     LIBRARIES
-        ZLIB::ZLIB
+        WrapZLIB::WrapZLIB
 )
 
 qt_internal_extend_target(BundledLibpng CONDITION NOT QT_FEATURE_system_zlib
diff --git a/src/corelib/CMakeLists.txt b/src/corelib/CMakeLists.txt
index 3c6b20636a..8351ec9263 100644
--- a/src/corelib/CMakeLists.txt
+++ b/src/corelib/CMakeLists.txt
@@ -692,7 +692,7 @@ qt_internal_extend_target(Core CONDITION ICC
 
 qt_internal_extend_target(Core CONDITION QT_FEATURE_system_zlib
     LIBRARIES
-        ZLIB::ZLIB
+        WrapZLIB::WrapZLIB
 )
 
 qt_internal_extend_target(Core CONDITION NOT QT_FEATURE_system_zlib
diff --git a/src/gui/CMakeLists.txt b/src/gui/CMakeLists.txt
index 31e727189b..a8692318eb 100644
--- a/src/gui/CMakeLists.txt
+++ b/src/gui/CMakeLists.txt
@@ -792,7 +792,7 @@ qt_internal_extend_target(Gui CONDITION ANDROID AND TEST_architecture_arch STREQ
 
 qt_internal_extend_target(Gui CONDITION QT_FEATURE_system_zlib
     LIBRARIES
-        ZLIB::ZLIB
+        WrapZLIB::WrapZLIB
 )
 
 qt_internal_extend_target(Gui CONDITION NOT QT_FEATURE_system_zlib
diff --git a/src/network/CMakeLists.txt b/src/network/CMakeLists.txt
index dc32520b32..e49b8d8930 100644
--- a/src/network/CMakeLists.txt
+++ b/src/network/CMakeLists.txt
@@ -136,7 +136,7 @@ qt_internal_extend_target(Network CONDITION QT_FEATURE_http AND QT_FEATURE_zstd
 
 qt_internal_extend_target(Network CONDITION QT_FEATURE_system_zlib
     LIBRARIES
-        ZLIB::ZLIB
+        WrapZLIB::WrapZLIB
 )
 
 qt_internal_extend_target(Network CONDITION NOT QT_FEATURE_system_zlib
diff --git a/src/tools/bootstrap/CMakeLists.txt b/src/tools/bootstrap/CMakeLists.txt
index a2f0e30920..7d1a067126 100644
--- a/src/tools/bootstrap/CMakeLists.txt
+++ b/src/tools/bootstrap/CMakeLists.txt
@@ -265,7 +265,7 @@ qt_internal_extend_target(Bootstrap CONDITION CMAKE_CROSSCOMPILING OR NOT QT_FEA
 
 qt_internal_extend_target(Bootstrap CONDITION QT_FEATURE_system_zlib AND NOT CMAKE_CROSSCOMPILING
     LIBRARIES
-        ZLIB::ZLIB
+        WrapZLIB::WrapZLIB
 )
 
 qt_internal_extend_target(Bootstrap CONDITION MINGW AND WIN32