Gcc: Suppress warnings in third_party

third_party/yasm/BUILD.gn

Index: third_party/yasm/BUILD.gn
diff --git a/third_party/yasm/BUILD.gn b/third_party/yasm/BUILD.gn
index 6f49a02a77f86866e355c32977bd24efeae231a6..adcb833184e15a75c21fb4bee53f149db550bf0b 100644
--- a/third_party/yasm/BUILD.gn
+++ b/third_party/yasm/BUILD.gn
@@ -202,6 +202,11 @@ if (current_toolchain == host_toolchain) {
         # reg3264type in x86expr.c is unused.
         "-Wno-unused-local-typedef",
       ]
+    } else if (is_linux) {
+      cflags = [
+        # dosexe_objfmt_output ignores the return value of ftruncate.
+        "-Wno-unused-result",
+      ]
     }
   }