Revert of [GN]: BUILD file housecleaning

tools/gn/ninja_binary_target_writer.cc

Index: tools/gn/ninja_binary_target_writer.cc
diff --git a/tools/gn/ninja_binary_target_writer.cc b/tools/gn/ninja_binary_target_writer.cc
index ae46760059fff7fbb1e7dadb27351a3af1188ccd..b7dace7ab0afcee76a7e287501c2d3e6374fe0e9 100644
--- a/tools/gn/ninja_binary_target_writer.cc
+++ b/tools/gn/ninja_binary_target_writer.cc
@@ -420,12 +420,16 @@ void NinjaBinaryTargetWriter::WriteCompilerVars(
     WriteOneFlag(SUBSTITUTION_ASMFLAGS, false, Toolchain::TYPE_NONE,
                  &ConfigValues::asmflags, opts);
   }
+  // TODO(andybons): Remove SOURCE_S and SOURCE_ASM checks once asmflags is
+  // used.
   if (used_types.Get(SOURCE_C) || used_types.Get(SOURCE_CPP) ||
-      used_types.Get(SOURCE_M) || used_types.Get(SOURCE_MM)) {
+      used_types.Get(SOURCE_M) || used_types.Get(SOURCE_MM) ||
+      used_types.Get(SOURCE_S) || used_types.Get(SOURCE_ASM)) {
     WriteOneFlag(SUBSTITUTION_CFLAGS, false, Toolchain::TYPE_NONE,
                  &ConfigValues::cflags, opts);
   }
-  if (used_types.Get(SOURCE_C)) {
+  if (used_types.Get(SOURCE_C) || used_types.Get(SOURCE_S) ||
+      used_types.Get(SOURCE_ASM)) {
     WriteOneFlag(SUBSTITUTION_CFLAGS_C, has_precompiled_headers,
                  Toolchain::TYPE_CC, &ConfigValues::cflags_c, opts);
   }