[cmake] [asan] Remove unnecessary gtest dep from dynamic tests

Remove the redundant dependency on 'gtest' target from the dynamic tests
in non-MSVC environment. The tests reuse compiled objects
from ASAN_INST_TEST_OBJECTS, and therefore they have been built against
gtest already.

This both fixes the spurious dependency on 'gtest' target that breaks
stand-alone builds, and brings the dynamic tests more in line with
regular tests which do not pass this dependency
to add_compiler_rt_test() through generate_compiler_rt_tests().

Differential Revision: https://reviews.llvm.org/D38840

llvm-svn: 315620