[gtest] fix cppinterop testing with builtin_gtest

[ferdymercury]

Fixes

0be6ecb#commitcomment-187438394

[linev]

Seems to be I got a glitch with incremental builds.

Now when I rebuild everything from scratch - cmake is happy.
Sorry for the noise

[github-actions]

Test Results

    22 files      22 suites   3d 11h 9m 33s ⏱️
 3 856 tests  3 856 ✅ 0 💤 0 ❌
77 072 runs  77 072 ✅ 0 💤 0 ❌

Results for commit 9db911d.

♻️ This comment has been updated with latest results.

[linev]

Probably one need to do this like in ROOT_FIND_REQUIRED_DEP macro.
There error message is generated like:

   message(SEND_ERROR "The required package ${PACKAGE_NAME} was not found. "
   "Please install it in the system (preferred), set the corresponding CMake search variable, "
   "or opt in to downloading it using '-D${BUILTIN_CONFIG_OPTION}=ON'.")

Just let provide same kind of message for enabling builtin_gtest.

One just need to avoid that ffind_package(GTest) is invoked

[ferdymercury]

Probably one need to do this like in ROOT_FIND_REQUIRED_DEP macro.

Ok for me to add this, but I think it's a separate issue. There are many builtins that do not have yet this behavior, it's only for

# Request explicit user opt-in for required "easy to self-install" dependencies

Maybe all builtins considered easy should be enabled at one, not just gtest.

[linev]

gtest and gmock are really available on all platforms.
So making error like for other common builtins should be ok.

[linev]

Your second commit goes in right direction.
But one need to remove related code from lines 1270..1300
And in macro ROOT_FIND_REQUIRED_DEP one should be able to provide version of GTest

[ferdymercury]

But one need to remove related code from lines 1270..1300
And in macro ROOT_FIND_REQUIRED_DEP one should be able to provide version of GTest

Done!

[linev]

Thanks!