REQUIRES in ASCII test

Author: ldionne

libcxx/test/libcxx/utilities/format/format.functions/ascii.pass.cpp

@@ -8,9 +8,7 @@
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: GCC-ALWAYS_INLINE-FIXME
 
-// What would be the best way to force the test with unicode disabled?
-// Force unicode to be disabled.
-// ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_HAS_NO_UNICODE
+// REQUIRES: libcpp-has-no-unicode
 
 // TODO FMT This test should not require std::to_chars(floating-point)
 // XFAIL: availability-fp_to_chars-missing

libcxx/test/libcxx/utilities/format/format.functions/escaped_output.ascii.pass.cpp

@@ -11,9 +11,7 @@
 // TODO FMT This test should not require std::to_chars(floating-point)
 // XFAIL: availability-fp_to_chars-missing
 
-// What would be the best way to force the test with unicode disabled?
-// Force unicode to be disabled.
-// ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_HAS_NO_UNICODE
+// REQUIRES: libcpp-has-no-unicode
 
 // <format>