[compiler-rt] Remove llvm_gtest dependency from unit tests

All these unit tests already include ${COMPILER_RT_GTEST_SOURCE} as an
input source file and the target llvm_gtest does not exist for
standalone builds. Currently the DEPS argument is ignored for standalone
builds so the missing target is not a problem, but as part of fixing a
build race for standalone builds I am planning to include those
dependencies in COMPILER_RT_TEST_STANDALONE_BUILD_LIBS configurations.

Reviewed By: vitalybuka

Pull Request: https://github.com/llvm/llvm-project/pull/83649