include extra_cflags* in the step description

gn/BUILD.gn

Index: gn/BUILD.gn
diff --git a/gn/BUILD.gn b/gn/BUILD.gn
index 26e80f8dfc45f9e1ab6cfb95116d6967a8c58d5f..cea57454a9a7ccbedd77d61ccdf745ff11c63ea9 100644
--- a/gn/BUILD.gn
+++ b/gn/BUILD.gn
@@ -73,7 +73,7 @@ toolchain("gcc_like") {
     outputs = [
       "{{source_out_dir}}/{{target_output_name}}.{{source_name_part}}.o",
     ]
-    description = "$cc ... -o {{output}}"
+    description = "$cc ... $extra_cflags $extra_cflags_c -o {{output}}"
   }
 
   tool("cxx") {
@@ -83,7 +83,7 @@ toolchain("gcc_like") {
     outputs = [
       "{{source_out_dir}}/{{target_output_name}}.{{source_name_part}}.o",
     ]
-    description = "$cxx ... -o {{output}}"
+    description = "$cxx ... $extra_cflags $extra_cflags_cc -o {{output}}"
   }
 
   tool("asm") {