ONNX will build googletest from a Git checkout.  Patch CMake to use our
googletest package and enable tests by default.

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0aa9fda2..a573170c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -22,7 +22,7 @@ option(BUILD_ONNX_PYTHON "Build Python binaries" OFF)
 option(ONNX_GEN_PB_TYPE_STUBS "Generate protobuf python type stubs" ON)
 option(ONNX_WERROR "Build with Werror" OFF)
 option(ONNX_COVERAGE "Build with coverage instrumentation" OFF)
-option(ONNX_BUILD_TESTS "Build ONNX C++ APIs Tests" OFF)
+option(ONNX_BUILD_TESTS "Build ONNX C++ APIs Tests" ON)
 option(ONNX_USE_LITE_PROTO "Use lite protobuf instead of full." OFF)
 option(ONNXIFI_ENABLE_EXT "Enable onnxifi extensions." OFF)
 if(NOT DEFINED ONNX_ML)
@@ -82,8 +82,10 @@ if(CMAKE_SYSTEM_NAME STREQUAL "AIX")
 endif()

 if(ONNX_BUILD_TESTS)
-  list(APPEND CMAKE_MODULE_PATH ${ONNX_ROOT}/cmake/external)
-  include(googletest)
+  find_package(GTest REQUIRED)
+  if(NOT GTest_FOUND)
+    message(FATAL_ERROR "cannot find googletest")
+  endif()
 endif()

 if((ONNX_USE_LITE_PROTO AND TARGET protobuf::libprotobuf-lite) OR ((NOT ONNX_USE_LITE_PROTO) AND TARGET protobuf::libprotobuf))
diff --git a/cmake/unittest.cmake b/cmake/unittest.cmake
index e29a93ff..ae146390 100644
--- a/cmake/unittest.cmake
+++ b/cmake/unittest.cmake
@@ -6,8 +6,8 @@ include(${ONNX_ROOT}/cmake/Utils.cmake)

 find_package(Threads)

-set(${UT_NAME}_libs ${googletest_STATIC_LIBRARIES})
-set(${ONNXIFI_TEST_DRIVER}_libs ${googletest_STATIC_LIBRARIES})
+set(${UT_NAME}_libs ${GTEST_LIBRARIES})
+set(${ONNXIFI_TEST_DRIVER}_libs ${GTEST_LIBRARIES})

 list(APPEND ${UT_NAME}_libs onnx)
 list(APPEND ${UT_NAME}_libs onnx_proto)
@@ -31,10 +31,10 @@ function(AddTest)
   list(REMOVE_DUPLICATES _UT_SOURCES)

   add_executable(${_UT_TARGET} ${_UT_SOURCES})
-  add_dependencies(${_UT_TARGET} onnx onnx_proto googletest)
+  add_dependencies(${_UT_TARGET} onnx onnx_proto)

   target_include_directories(${_UT_TARGET}
-                             PUBLIC ${googletest_INCLUDE_DIRS}
+                             PUBLIC ${GTEST_INCLUDE_DIRS}
                                     ${ONNX_INCLUDE_DIRS}
                                     ${PROTOBUF_INCLUDE_DIRS}
                                     ${ONNX_ROOT}
stall.scm?id=329bd33fb849eb5e87070efe4c52259dd509110b'>install.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/build/install.scm?id=329bd33fb849eb5e87070efe4c52259dd509110b&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-12-15 17:32:10 +0100'>2020-12-15</span></td><td><a href='/guix/commit/gnu/build/install.scm?id=6a060ff27ff68384d7c90076baa36c349fff689d'>store-copy: 'populate-store' can optionally deduplicate files.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-09-02 17:05:22 +0200'>2020-09-02</span></td><td><a href='/guix/commit/gnu/build/install.scm?id=22827396baea149f193f6e9558b522e6d9c89a44'>install: Factorize cow-store procedure.</a><span class='msg-avail'>...</span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2020-05-05 20:43:21 +0200'>2020-05-05</span></td><td><a href='/guix/commit/gnu/build/install.scm?id=87a40d7203a813921b3ef0805c2b46c0026d6c31'>Merge branch 'master' into core-updates</a></td><td>Marius Bakke</td></tr>
<tr><td><span title='2020-05-05 16:13:53 +0200'>2020-05-05</span></td><td><a href='/guix/commit/gnu/build/install.scm?id=f19cf27c2b9ff92e2c0fd931ef7fde39c376adaa'>image: Add a new API.</a><span class='msg-avail'>...</span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2020-05-05 16:08:33 +0200'>2020-05-05</span></td><td><a href='/guix/commit/gnu/build/install.scm?id=892bbea750e5733979ee0423cbdfcea222b07925'>build: install: Do not set store GID.</a><span class='msg-avail'>...</span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2020-05-05 16:08:32 +0200'>2020-05-05</span></td><td><a href='/guix/commit/gnu/build/install.scm?id=5990e95b607b888edd862a2ccb5ca69dcd17d801'>build: install: Ignore chown exceptions.</a><span class='msg-avail'>...</span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2020-04-11 19:22:25 +0200'>2020-04-11</span></td><td><a href='/guix/commit/gnu/build/install.scm?id=87241947aa2c0148a6f06989057a113c57ea9208'>install: 'populate-root-file-system' can be passed extra directives.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>