[build] Remove a stray comment. NFC

The CMake change associated with this comment was removed but the
comment got left behind. Add a newline instead.

llvm-svn: 353793

llvm/runtimes/CMakeLists.txt

@@ -101,7 +101,7 @@ if(${CMAKE_SOURCE_DIR} STREQUAL ${CMAKE_CURRENT_SOURCE_DIR})
 
   # Avoid checking whether the compiler is working.
   set(LLVM_COMPILER_CHECKED ON)
-  # Mark the compiler as compatible with GCC.
+
   # Enable warnings, otherwise -w gets added to the cflags by HandleLLVMOptions
   # resulting in unjustified successes by check_cxx_compiler_flag.
   set(LLVM_ENABLE_WARNINGS ON)