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)
packages/agda.scm'>
<input type='hidden' name='id' value='4532e7f415c6116c74f8bc231fc78e4c8bdae848'/><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=4532e7f415c6116c74f8bc231fc78e4c8bdae848'>root</a>/<a href='/guix/log/gnu?id=4532e7f415c6116c74f8bc231fc78e4c8bdae848'>gnu</a>/<a href='/guix/log/gnu/packages?id=4532e7f415c6116c74f8bc231fc78e4c8bdae848'>packages</a>/<a href='/guix/log/gnu/packages/agda.scm?id=4532e7f415c6116c74f8bc231fc78e4c8bdae848'>agda.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/packages/agda.scm?id=4532e7f415c6116c74f8bc231fc78e4c8bdae848&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2023-02-26 10:20:14 +0100'>2023-02-26</span></td><td><a href='/guix/commit/gnu/packages/agda.scm?id=890a181ed1766b433b5bfe1a3419b50ffa6503cb'>gnu: Use HACKAGE-URI for packages from Hackage.</a><span class='msg-avail'>...<span class='msg-tooltip'>Script-aided bulk change.
</span></span></td><td>Lars-Dominik Braun</td></tr>
<tr><td><span title='2023-02-26 10:20:11 +0100'>2023-02-26</span></td><td><a href='/guix/commit/gnu/packages/agda.scm?id=cad6aa8082e99fe60570e3fd53a0e5876a8f243e'>gnu: Add upstream-name property to Haskell packages.</a><span class='msg-avail'>...<span class='msg-tooltip'>Script-aided bulk change.
</span></span></td><td>Lars-Dominik Braun</td></tr>
<tr><td><span title='2023-02-16 22:41:03 +0200'>2023-02-16</span></td><td><a href='/guix/commit/gnu/packages/agda.scm?id=672036c6dfe508810b565f4cf38e4f2aad2f7151'>gnu: Remove unneeded module imports.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/abiword.scm,
* gnu/packages/ada.scm,
* gnu/packages/agda.scm,
* gnu/packages/backup.scm,
* gnu/packages/barrier.scm,
* gnu/packages/bioinformatics.scm,
* gnu/packages/bootstrap.scm,
* gnu/packages/bqn.scm,
* gnu/packages/c.scm,
* gnu/packages/chemistry.scm,
* gnu/packages/coq.scm,
* gnu/packages/cross-base.scm,
* gnu/packages/databases.scm,
* gnu/packages/emacs-xyz.scm,
* gnu/packages/enlightenment.scm,
* gnu/packages/games.scm,
* gnu/packages/geo.scm,
* gnu/packages/ghostscript.scm,
* gnu/packages/gl.scm,
* gnu/packages/golang.scm,
* gnu/packages/jami.scm,
* gnu/packages/java-maths.scm,
* gnu/packages/kde-frameworks.scm,
* gnu/packages/kde-plasma.scm,
* gnu/packages/language.scm,
* gnu/packages/libreoffice.scm,
* gnu/packages/linphone.scm,
* gnu/packages/lisp.scm,
* gnu/packages/llvm.scm,
* gnu/packages/machine-learning.scm,
* gnu/packages/minetest.scm,
* gnu/packages/monitoring.scm,
* gnu/packages/nfs.scm,
* gnu/packages/ocr.scm,
* gnu/packages/opencl.scm,
* gnu/packages/pdf.scm,
* gnu/packages/python-xyz.scm,
* gnu/packages/racket.scm,
* gnu/packages/rust.scm,
* gnu/packages/syncthing.scm,
* gnu/packages/syndication.scm,
* gnu/packages/telegram.scm,
* gnu/packages/vulkan.scm,
* gnu/packages/web-browsers.scm,
* gnu/packages/web.scm,
* gnu/packages/webkit.scm: Remove some unecessary module imports.
</span></span></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2022-05-12 08:42:09 +0300'>2022-05-12</span></td><td><a href='/guix/commit/gnu/packages/agda.scm?id=2e0d02ebe351024cd97911cb1e5e1a6af1edc7f0'>gnu: agda.scm: Add missing import.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/agda.scm: Also use (guix gexp).
</span></span></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2022-05-08 02:00:00 +0200'>2022-05-08</span></td><td><a href='/guix/commit/gnu/packages/agda.scm?id=914d2c2142eb22a0219cf09475ea7207808ded6a'>gnu: agda: Use G-expressions.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/agda.scm (agda)[arguments]:
Rewrite as G-expressions.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2022-05-08 02:00:00 +0200'>2022-05-08</span></td><td><a href='/guix/commit/gnu/packages/agda.scm?id=2c67e1cfbf5dc4c528f9ddb5dce843bd8326cdab'>gnu: agda: Update to 2.6.2.2.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/agda.scm (agda): Update to 2.6.2.2.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>