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)
ame='id' value='9be28375cf6d900e075b470412d629ddbd8710c0'/><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=9be28375cf6d900e075b470412d629ddbd8710c0'>root</a>/<a href='/guix/log/tests?id=9be28375cf6d900e075b470412d629ddbd8710c0'>tests</a>/<a href='/guix/log/tests/graph.scm?id=9be28375cf6d900e075b470412d629ddbd8710c0'>graph.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/tests/graph.scm?id=9be28375cf6d900e075b470412d629ddbd8710c0&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2023-04-07 17:53:37 +0200'>2023-04-07</span></td><td><a href='/guix/commit/tests/graph.scm?id=acdb42e5d09a504d521d8b632c2c4a66d70f94e4'>gnu: Purge pre-1.3.0 deprecated packages.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/bioinformatics.scm (deeptools): Remove variable.
* gnu/packages/efi.scm (efi_analyzer): Ditto.
* gnu/packages/guile.scm (guile-2.2/bug-fix, guile-json): Ditto.
* gnu/packages/image.scm (libjpeg): Ditto.
* gnu/packages/kde.scm (kdevplatform): Ditto
* gnu/packages/linphone.scm (linphoneqt): Ditto.
* gnu/packages/maths.scm (blis-sandybridge, blis-haswell, blis-knl): Ditto.
* gnu/packages/mpi.scm (hwloc-2.0): Ditto.
* gnu/packages/music.scm (python-abjad, zlfo): Ditto.
* gnu/packages/perl.scm (perl-base, perl-parent): Ditto.
* gnu/packages/tryton.scm (python-trytond): Ditto.
* gnu/packages/video.scm (gnome-mpv): Ditto.
* tests/graph.scm: Use guile-json-1.

Signed-off-by: Ludovic Courtès &lt;ludo@gnu.org&gt;
</span></span></td><td>Bruno Victal</td></tr>
<tr><td><span title='2022-10-22 01:46:55 +0200'>2022-10-22</span></td><td><a href='/guix/commit/tests/graph.scm?id=a3619079f95213c4f983e69210ed12b38fd31022'>Remove now unnecessary uses of (guix grafts).</a><span class='msg-avail'>...<span class='msg-tooltip'>These modules would use (guix grafts) just to access '%graft?' and
related bindings, which are now in (guix store).

* gnu/ci.scm,
guix/gexp.scm,
guix/lint.scm,
guix/scripts.scm,
guix/scripts/archive.scm,
guix/scripts/build.scm,
guix/scripts/challenge.scm,
guix/scripts/deploy.scm,
guix/scripts/environment.scm,
guix/scripts/home.scm,
guix/scripts/pack.scm,
guix/scripts/package.scm,
guix/scripts/pull.scm,
guix/scripts/size.scm,
guix/scripts/system.scm,
guix/scripts/weather.scm,
tests/builders.scm,
tests/channels.scm,
tests/cpan.scm,
tests/derivations.scm,
tests/gexp.scm,
tests/graph.scm,
tests/guix-daemon.sh,
tests/monads.scm,
tests/pack.scm,
tests/packages.scm,
tests/profiles.scm,
tests/system.scm: Remove #:use-module (guix grafts).
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-07-01 23:29:16 +0200'>2022-07-01</span></td><td><a href='/guix/commit/tests/graph.scm?id=bee2c369fa2a3d51e6a1218d1b1a0ee86528674a'>tests: Adjust 'guix graph' test to latest OCaml changes.</a><span class='msg-avail'>...<span class='msg-tooltip'>* tests/graph.scm ("reverse bag DAG"): Adjust to latest OCaml changes by
looking at dune/ocaml-camomile/ocaml-utop.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-02-05 08:02:30 +0100'>2022-02-05</span></td><td><a href='/guix/commit/tests/graph.scm?id=45082b9a8c12af285f4386538fc7acc4668cb11c'>tests: Assert that cyclic graphs can be produced.</a><span class='msg-avail'>...<span class='msg-tooltip'>* tests/graph.scm ("package DAG, oops it was a cycle"): New test.
</span></span></td><td>Liliana Marie Prikler</td></tr>
<tr><td><span title='2021-09-21 15:15:52 +0200'>2021-09-21</span></td><td><a href='/guix/commit/tests/graph.scm?id=5b32ad4f6f555d305659cee825879df075b06331'>graph: Add '--max-depth'.</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/graph.scm (export-graph): Add #:max-depth and honor it, adding
'depths' argument to 'loop'.
* guix/scripts/graph.scm (%options, show-help): Add '--max-depth'.
(%default-options): Add 'max-depth'.
(guix-graph): Pass #:max-depth to 'export-graph'.
* tests/graph.scm ("package DAG, limited depth"): New test.
* doc/guix.texi (Invoking guix graph): Document it.
</span></span></td><td>Ludovic Courtès</td></tr>