Use shared gtest instead of submodule

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 617e4b2..2857875 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -18,7 +18,6 @@ set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_SOURCE_DIR}/cmake/Modules/")
 include(GNUInstallDirs)
 
 project(leelaz)
-add_subdirectory(gtest EXCLUDE_FROM_ALL) # We don't want to install gtest, exclude it from `all`
 
 # Required Packages
 set(Boost_MIN_VERSION "1.58.0")
@@ -27,6 +26,7 @@ find_package(Boost 1.58.0 REQUIRED program_options filesystem)
 find_package(Threads REQUIRED)
 find_package(ZLIB REQUIRED)
 find_package(OpenCL REQUIRED)
+find_package(GTest REQUIRED)
 # We need OpenBLAS for now, because we make some specific
 # calls. Ideally we'd use OpenBLAS is possible and fall back to
 # not doing those calls if it's not present.
@@ -93,6 +93,7 @@ include_directories(${IncludePath})
 include_directories(${Boost_INCLUDE_DIRS})
 include_directories(${OpenCL_INCLUDE_DIRS})
 include_directories(${ZLIB_INCLUDE_DIRS})
+include_directories(${GTEST_INCLUDE_DIRS})
 
 if((UNIX AND NOT APPLE) OR WIN32)
     include_directories(${BLAS_INCLUDE_DIRS})
@@ -141,7 +142,8 @@ target_link_libraries(tests ${Boost_LIBRARIES})
 target_link_libraries(tests ${BLAS_LIBRARIES})
 target_link_libraries(tests ${OpenCL_LIBRARIES})
 target_link_libraries(tests ${ZLIB_LIBRARIES})
-target_link_libraries(tests gtest_main ${CMAKE_THREAD_LIBS_INIT})
+target_link_libraries(tests ${GTEST_BOTH_LIBRARIES})
+target_link_libraries(tests ${CMAKE_THREAD_LIBS_INIT})
 
 include(GetGitRevisionDescription)
 git_describe(VERSION --tags)
scm'>
<input type='hidden' name='id' value='ef077b83f9de49c6f162eddb6ccd61f3d78e591f'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=ef077b83f9de49c6f162eddb6ccd61f3d78e591f'>root</a>/<a href='/guix/log/gnu?id=ef077b83f9de49c6f162eddb6ccd61f3d78e591f'>gnu</a>/<a href='/guix/log/gnu/tests?id=ef077b83f9de49c6f162eddb6ccd61f3d78e591f'>tests</a>/<a href='/guix/log/gnu/tests/image.scm?id=ef077b83f9de49c6f162eddb6ccd61f3d78e591f'>image.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/tests/image.scm?id=ef077b83f9de49c6f162eddb6ccd61f3d78e591f&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2023-07-07 21:14:10 +0200'>2023-07-07</span></td><td><a href='/guix/commit/gnu/tests/image.scm?id=209204e23b39af09e0ea92540b6fa00a60e6a0ae'>image: Prefer gpt partition table for efi images</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/system/image.scm (efi-disk-image): Use gpt partition-table-type.
(efi32-disk-image): Use gpt partition-table-type.
(qcow2-image-type): Use mbr partition-table-type explicitly.
* gnu/tests/image.scm: Assert partition table type of efi-disk-image.

Signed-off-by: Josselin Poiret &lt;dev@jpoiret.xyz&gt;
</span></span></td><td>Sergey Trofimov</td></tr>
<tr><td><span title='2022-08-30 19:29:58 +0200'>2022-08-30</span></td><td><a href='/guix/commit/gnu/tests/image.scm?id=73fb14c28ae883b6bd22ffdc63d1d59752cb8e0e'>tests: image: New test.</a><span class='msg-avail'>...<span class='msg-tooltip'>Add a new image test module to validate the image creation itself. The images
structures are validated using guile-parted. Checking the content of those
images is out of scope and should be performed in other modules (installation
for instance).

* gnu/tests/image.scm: New file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add it.
</span></span></td><td>Mathieu Othacehe</td></tr>