* Added FindGTest with GMock targets

* GTest will be downloaded as external project if needed

cmake/FindGTest.cmake

@@ -0,0 +1,117 @@
+Function ( __gtest_define_backwards_compatible_library_targets )
+    Set ( GTEST_BOTH_LIBRARIES ${GTEST_LIBRARIES} ${GTEST_MAIN_LIBRARIES} PARENT_SCOPE )
+
+    # Add targets mapping the same library names as defined in
+    # older versions of CMake's FindGTest
+    If ( NOT TARGET GTest::GTest )
+        Add_Library ( GTest::GTest INTERFACE IMPORTED )
+        Target_Link_Libraries ( GTest::GTest INTERFACE GTest::gtest )
+    EndIf ()
+    If ( NOT TARGET GTest::Main )
+        Add_Library ( GTest::Main INTERFACE IMPORTED )
+        Target_Link_Libraries ( GTest::Main INTERFACE GTest::gtest_main )
+    EndIf ()
+
+    If ( NOT TARGET GMock::GMock )
+        Add_Library ( GMock::GMock INTERFACE IMPORTED )
+        Target_Link_Libraries ( GMock::GMock INTERFACE GMock::gmock )
+    EndIf ()
+    If ( NOT TARGET GMock::Main )
+        Add_Library ( GMock::Main INTERFACE IMPORTED )
+        Target_Link_Libraries ( GMock::Main INTERFACE GMock::gmock_main )
+    EndIf ()
+EndFunction()
+
+Include ( ExternalProject )
+Include ( FindPackageHandleStandardArgs )
+
+If( CMAKE_CROSSCOMPILING )
+    Message ( STATUS "Disable search for 'GTest' package because of cross compiling. Skip unit test targets..." )
+    Return ( )
+EndIf ( )
+
+If( GTest_FOUND )
+    Message ( FATAL_ERROR "GTest already found! Do not expect that an other CMake script looked for 'GTest'. " )
+EndIf ( )
+
+# Configure external project
+Set ( GTEST_EX_PATH "${CMAKE_BINARY_DIR}/subprojects/googletest" )
+Get_Property ( IS_INCLUDED GLOBAL PROPERTY __external_project_googletest )
+If ( NOT IS_INCLUDED )
+    ExternalProject_Add (
+        project_googletest
+        URL "https://github.com/google/googletest/archive/refs/tags/release-1.10.0.tar.gz"
+        URL_HASH SHA256=9dc9157a9a1551ec7a7e43daea9a694a0bb5fb8bec81235d8a1e6ef64c716dcb
+        PREFIX ${GTEST_EX_PATH}
+        INSTALL_COMMAND make install DESTDIR=${GTEST_EX_PATH} )
+    Set_Property ( GLOBAL PROPERTY __external_project_googletest TRUE )
+EndIf ( )
+
+Set ( GTEST_INCLUDE_DIR "${GTEST_EX_PATH}/usr/local/include" )
+Set ( GTEST_LIBRARY "${GTEST_EX_PATH}/usr/local/lib/libgtest.a" )
+Set ( GTEST_MAIN_LIBRARY "${GTEST_EX_PATH}/usr/local/lib/libgtest_main.a" )
+Set ( GMOCK_LIBRARY "${GTEST_EX_PATH}/usr/local/lib/libgmock.a" )
+Set ( GMOCK_MAIN_LIBRARY "${GTEST_EX_PATH}/usr/local/lib/libgmock_main.a" )
+File ( MAKE_DIRECTORY ${GTEST_INCLUDE_DIR} )
+
+# Find package
+Find_Package_Handle_Standard_Args ( GTest
+                                    DEFAULT_MSG
+                                    GTEST_INCLUDE_DIR
+                                    GTEST_LIBRARY
+                                    GTEST_MAIN_LIBRARY
+                                    GMOCK_LIBRARY
+                                    GMOCK_MAIN_LIBRARY )
+
+If ( GTest_FOUND )
+
+    Set ( GTEST_INCLUDE_DIRS ${GTEST_INCLUDE_DIR} )
+
+    Find_Package ( Threads QUIET )
+
+    If ( NOT TARGET GTest::gtest )
+        Add_Library ( GTest::gtest STATIC IMPORTED )
+        Add_Dependencies ( GTest::gtest project_googletest )
+        If ( TARGET Threads::Threads )
+            Set_Target_Properties ( GTest::gtest PROPERTIES
+                INTERFACE_LINK_LIBRARIES Threads::Threads )
+        EndIf ()
+        Set_Target_Properties ( GTest::gtest
+                                PROPERTIES
+                                    INTERFACE_INCLUDE_DIRECTORIES "${GTEST_INCLUDE_DIRS}"
+                                    IMPORTED_LOCATION "${GTEST_LIBRARY}" )
+    EndIf ()
+
+    If ( NOT TARGET GTest::gtest_main )
+        Add_Library ( GTest::gtest_main STATIC IMPORTED )
+        Set_Target_Properties ( GTest::gtest_main
+                                PROPERTIES
+                                    INTERFACE_INCLUDE_DIRECTORIES "${GTEST_INCLUDE_DIRS}"
+                                    INTERFACE_LINK_LIBRARIES "GTest::gtest"
+                                    IMPORTED_LOCATION "${GTEST_MAIN_LIBRARY}" )
+    EndIf()
+
+    If ( NOT TARGET GMock::gmock )
+        Add_Library ( GMock::gmock STATIC IMPORTED )
+        If ( TARGET Threads::Threads )
+            Set_Target_Properties ( GMock::gmock PROPERTIES
+                INTERFACE_LINK_LIBRARIES Threads::Threads )
+        EndIf ()
+        Set_Target_Properties ( GMock::gmock
+                                PROPERTIES
+                                    INTERFACE_INCLUDE_DIRECTORIES "${GTEST_INCLUDE_DIRS}"
+                                    INTERFACE_LINK_LIBRARIES "GTest::gtest"
+                                    IMPORTED_LOCATION "${GMOCK_LIBRARY}" )
+    EndIf ()
+
+    If ( NOT TARGET GMock::gmock_main )
+        Add_Library ( GMock::gmock_main STATIC IMPORTED )
+        Set_Target_Properties ( GMock::gmock_main
+                                PROPERTIES
+                                    INTERFACE_INCLUDE_DIRECTORIES "${GTEST_INCLUDE_DIRS}"
+                                    INTERFACE_LINK_LIBRARIES "GMock::gmock"
+                                    IMPORTED_LOCATION "${GMOCK_MAIN_LIBRARY}" )
+    EndIf()
+
+    __gtest_define_backwards_compatible_library_targets ()
+EndIf ()