Prepare for |is_posix| switch in the Fuchsia build in yasm/

|is_posix| will be switched to false for Fuchsia, this is a preliminary change.

Bug: 812974
Change-Id: I682e0aca08051f4c930ea7b3435bdf3ca0c91d2b
Reviewed-on: https://chromium-review.googlesource.com/988811
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: Fabrice de Gans-Riberi <fdegans@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#548195}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 30efd932c4641a19e91dfe9c23265580e7b0d994
diff --git a/BUILD.gn b/BUILD.gn
index e403dee..ab2f941 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -72,7 +72,7 @@
       "source/patched-yasm",
     ]
     defines = [ "HAVE_CONFIG_H" ]
-    if (is_posix) {
+    if (is_posix || is_fuchsia) {
       cflags = [ "-std=gnu99" ]
     }
   }
diff --git a/yasm_assemble.gni b/yasm_assemble.gni
index 73d5548..07bf5f9 100644
--- a/yasm_assemble.gni
+++ b/yasm_assemble.gni
@@ -55,7 +55,7 @@
       "amd64",
     ]
   }
-} else if (is_posix) {
+} else if (is_posix || is_fuchsia) {
   if (current_cpu == "x86") {
     _yasm_flags = [
       "-felf32",