CMake: Exclude test-related depends when building tests

When building without tests, GTest and GMock are not needed. This change
allows build systems to continue with filecoin compilation without devoting
resources to its testing infrastructure.

Author: eigendude

cmake/dependencies.cmake

@@ -1,10 +1,12 @@
 # hunter dependencies
 # https://docs.hunter.sh/en/latest/packages/
 
-# https://docs.hunter.sh/en/latest/packages/pkg/GTest.html
-hunter_add_package(GTest)
-find_package(GTest CONFIG REQUIRED)
-find_package(GMock CONFIG REQUIRED)
+if (TESTING)
+  # https://docs.hunter.sh/en/latest/packages/pkg/GTest.html
+  hunter_add_package(GTest)
+  find_package(GTest CONFIG REQUIRED)
+  find_package(GMock CONFIG REQUIRED)
+endif()
 
 # https://docs.hunter.sh/en/latest/packages/pkg/Boost.html
 hunter_add_package(Boost COMPONENTS date_time filesystem random)