Adapt Android toolchain file and FindGradle to Qt6

- We don't need the Threads target workaround anymore, that breaks the
build with Qt6 even.
- The Gradle wrapper shipped with Qt is no longer installed as executable,
so we need to run this in sh explicitly.
- Qt6 uses a different Android Gradle plugin version (not to be confused
with the Gradle version), which we need to make available for the
configure_file() call on the build.gradle file.

With this most Framework modules build against Qt6 here.

2 files changed, 21 insertions, 4 deletions

diff --git a/find-modules/FindGradle.cmake b/find-modules/FindGradle.cmake
index 6d8d6929..792598ed 100644
--- a/find-modules/FindGradle.cmake
+++ b/find-modules/FindGradle.cmake
@@ -27,18 +27,24 @@ Installs a Android AAR library that has been created with ``gradle_add_aar``.
 Since 5.76.0.
 #]=======================================================================]
 
+include(${CMAKE_CURRENT_LIST_DIR}/../modules/QtVersionOption.cmake)
 include(CMakeParseArguments)
 include(FindPackageHandleStandardArgs)
 
-find_package(Qt5Core REQUIRED)
+find_package(Qt${QT_MAJOR_VERSION}Core REQUIRED)
 
+set (Gradle_PRECOMMAND "")
 if (NOT WIN32)
     set(Gradle_EXECUTABLE ${CMAKE_BINARY_DIR}/gradle/gradlew)
+    # the gradlew script installed by Qt6 is not executable, so running it directly fails
+    if (QT_MAJOR_VERSION EQUAL "6")
+        set(Gradle_PRECOMMAND "sh")
+    endif()
 else()
     set(Gradle_EXECUTABLE ${CMAKE_BINARY_DIR}/gradle/gradlew.bat)
 endif()
 
-get_target_property(_qt_core_location Qt5::Core LOCATION)
+get_target_property(_qt_core_location Qt${QT_MAJOR_VERSION}::Core LOCATION)
 get_filename_component(_qt_install_root ${_qt_core_location} DIRECTORY)
 get_filename_component(_qt_install_root ${_qt_install_root}/../ ABSOLUTE)
 
@@ -50,6 +56,13 @@ add_custom_command(OUTPUT ${Gradle_EXECUTABLE}
 )
 add_custom_target(gradle DEPENDS ${Gradle_EXECUTABLE})
 
+# Android Gradle plugin version (not the Gradle version!) used by Qt, for use in our own build.gradle files
+if (QT_MAJOR_VERSION EQUAL "5")
+    set(Gradle_ANDROID_GRADLE_PLUGIN_VERSION 3.6.4)
+else()
+    set(Gradle_ANDROID_GRADLE_PLUGIN_VERSION 7.0.2)
+endif()
+
 find_package_handle_standard_args(Gradle DEFAULT_MSG Gradle_EXECUTABLE)
 
 function(gradle_add_aar target)
@@ -71,7 +84,7 @@ function(gradle_add_aar target)
     file(GLOB_RECURSE _src_files CONFIGURE_DEPENDS "*")
     add_custom_command(
         OUTPUT ${_build_root}/build/outputs/aar/${ARG_NAME}${_aar_suffix}.aar
-        COMMAND ${Gradle_EXECUTABLE} ${_aar_gradleCmd}
+        COMMAND ${Gradle_PRECOMMAND} ${Gradle_EXECUTABLE} ${_aar_gradleCmd}
         # this allows make create-apk to work without installations for apps with AAR libs in the same repository
         COMMAND ${CMAKE_COMMAND} -E copy ${_build_root}/build/outputs/aar/${ARG_NAME}${_aar_suffix}.aar ${CMAKE_BINARY_DIR}/jar/${ARG_NAME}.aar
         DEPENDS ${Gradle_EXECUTABLE} ${_src_files}
diff --git a/toolchain/Android.cmake b/toolchain/Android.cmake
index 5a48464c..280f129d 100644
--- a/toolchain/Android.cmake
+++ b/toolchain/Android.cmake
@@ -179,7 +179,11 @@ endif()
 # armv7 really doesn't like mixing PIC/PIE code.
 # Since we only have to care about a single compiler,
 # hard-code the values here.
-if (NOT TARGET Threads::Threads)
+# Qt6 fixes this and breaks if we define Threads::Threads here.
+# We cannot use our usual Qt version check at this point though yet,
+# se check whether we are chainloaded by the Qt toolchain as an indicator
+# for Qt6.
+if (NOT TARGET Threads::Threads AND NOT DEFINED __qt_chainload_toolchain_file)
     set(Threads_FOUND TRUE)
     set(CMAKE_THREAD_LIBS_INIT "-pthread")
     add_library(Threads::Threads INTERFACE IMPORTED)