create fallback gtest subproject dependency

Allows project to be built and tested locally.

Signed-off-by: Zane Shelley <zshelle@us.ibm.com>
Change-Id: I0965581e5b2bc006a0edfcd05a6fea996f3f6ec2
diff --git a/test/meson.build b/test/meson.build
index e780a2e..cbe7fbc 100644
--- a/test/meson.build
+++ b/test/meson.build
@@ -1,3 +1,25 @@
+# Get the gtest/gmock dependencies.
+gtest_dep = dependency('gtest', main: true, disabler: true, required: false)
+gmock_dep = dependency('gmock', disabler: true, required: false)
+if not gtest_dep.found() or not gmock_dep.found()
+    cmake = import('cmake')
+    gtest_proj = cmake.subproject('googletest',
+                                  required: false)
+    if gtest_proj.found()
+        gtest_dep = declare_dependency(
+            dependencies: [
+                dependency('threads'),
+                gtest_proj.dependency('gtest'),
+                gtest_proj.dependency('gtest_main'),
+            ]
+        )
+        gmock_dep = gtest_proj.dependency('gmock')
+    else
+        assert(not get_option('tests').enabled(),
+               'Googletest is required if tests are enabled')
+    endif
+endif
+
 # build simulator
 subdir('simulator')
 
@@ -12,13 +34,9 @@
     'operator_register_test',
 ]
 
-gtest = dependency('gtest', main : true, required : false, method : 'system')
-
-if gtest.found()
-    foreach g : gtests
-        test(g, executable(g.underscorify(), g + '.cpp', test_src, \
-                            dependencies : gtest, \
-                            include_directories : incdir))
-  endforeach
-endif
+foreach g : gtests
+  test(g, executable(g.underscorify(), g + '.cpp', test_src,
+                     dependencies : gtest_dep,
+                     include_directories : incdir))
+endforeach