Update LLVMLibCTestRules.cmake

Author: vinay-deshmukh

libc/cmake/modules/LLVMLibCTestRules.cmake

@@ -1,5 +1,9 @@
 function(_get_common_test_compile_options output_var c_test flags)
   _get_compile_options_from_flags(compile_flags ${flags})
+  # Remove -fno-math-errno if it was added.
+  if(LIBC_ADD_FNO_MATH_ERRNO)
+    list(REMOVE_ITEM compile_options "-fno-math-errno")
+  endif()
 
   set(compile_options
       ${LIBC_COMPILE_OPTIONS_DEFAULT}