[infra/onert] Update GTest version and download configuration (#16119)

- Update GTest URL from release-1.12.1 to v1.15.2
- Add DIRNAME parameter to ExternalSource_Download to specify directory name as GTEST-1.15.2

ONE-DCO-1.0-Signed-off-by: Hyeongseok Oh <[email protected]>

Author: hseok-oh

runtime/infra/cmake/packages/GTestSourceConfig.cmake

@@ -8,9 +8,12 @@ function(_GTestSource_import)
   nnfw_include(OptionTools)
 
   envoption(EXTERNAL_DOWNLOAD_SERVER "https://github.com")
-  envoption(GTEST_URL ${EXTERNAL_DOWNLOAD_SERVER}/google/googletest/archive/release-1.12.1.tar.gz)
+  envoption(GTEST_URL ${EXTERNAL_DOWNLOAD_SERVER}/google/googletest/archive/v1.15.2.tar.gz)
 
-  ExternalSource_Download(GTEST ${GTEST_URL})
+  ExternalSource_Download(GTEST
+    DIRNAME GTEST-1.15.2
+    URL ${GTEST_URL}
+  )
 
   set(GTestSource_DIR ${GTEST_SOURCE_DIR} PARENT_SCOPE)
   set(GTestSource_FOUND TRUE PARENT_SCOPE)