Remove leftover artifacts from use of gtest.

libc/cmake/modules/LLVMLibCRules.cmake

function(add_redirector_library target_name)
 
   set_target_properties(
     ${target_name}
     PROPERTIES
       LINKER_LANGUAGE "C"
   )
 endfunction(add_redirector_library)
 
-# Rule to add a gtest unittest.
+# Rule to add a libc unittest.
 # Usage
 #    add_libc_unittest(
 #      <target name>
 #      SUITE <name of the suite this test belongs to>
 #      SRCS  <list of .cpp files for the test>
 #      HDRS  <list of .h files for the test>
 #      DEPENDS <list of dependencies>
 #    )
if(library_deps)
     target_link_libraries(${target_name} PRIVATE ${library_deps})
   endif()
 
   set_target_properties(${target_name} PROPERTIES RUNTIME_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
 
   add_dependencies(
     ${target_name}
     ${LIBC_UNITTEST_DEPENDS}
-    gtest
   )
 
   target_link_libraries(${target_name} PRIVATE LibcUnitTest)
 
   add_custom_command(
     TARGET ${target_name}
     POST_BUILD
     COMMAND $<TARGET_FILE:${target_name}>