googletest/cmake: Use pw_add_error_target
googletest/cmake: Use pw_add_error_target

Refactors the CMake rules for googletest to use pw_add_error_target.

Change-Id: Ic747570c73085fb68d98fd294642953327be5158
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/118672
Pigweed-Auto-Submit: Ewout van Bekkum <638f134dbc68778d6b859fb04a64baea2b00b021@google.com>
Commit-Queue: Auto-Submit <14637eda5603879df170705285bf30f5996692f0@pigweed.google.com.iam.gserviceaccount.com>
Reviewed-by: Armando Montanez <97ef6fdb231c129ac8827d9f0c4106bfbf57f74f@google.com>

google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed