When building chrome/win on non-win, make sure is_win is true while running grit.

tools/grit/grit_rule.gni

Index: tools/grit/grit_rule.gni
diff --git a/tools/grit/grit_rule.gni b/tools/grit/grit_rule.gni
index 68e5976fe1630a8a9b036295aec96b17ab2c4c63..90c0b00abbf925d383a421972f4ea6295ace52b0 100644
--- a/tools/grit/grit_rule.gni
+++ b/tools/grit/grit_rule.gni
@@ -182,8 +182,6 @@ if (enable_image_loader_extension) {
 
 if (is_android) {
   grit_defines += [
-    "-t",
-    "android",
     "-E",
     "ANDROID_JAVA_TAGGED_ONLY=true",
   ]
@@ -196,11 +194,38 @@ if (is_mac || is_ios) {
   ]
 }
 
-if (is_ios) {
-  grit_defines += [
-    "-t",
-    "ios",
-  ]
+# When cross-compiling, explicitly pass the target system to grit.
+if (current_toolchain != host_toolchain) {
+  if (is_android) {
+    grit_defines += [
+      "-t",
+      "android",
+    ]

[Nico, 2016/04/04 01:36:08]

I wish `gn format` allowed `    grit_defines += [ "-t", "android" ]`, then this
file would be 88 lines shorter

+  }
+  if (is_ios) {
+    grit_defines += [
+      "-t",
+      "ios",
+    ]
+  }
+  if (is_linux) {
+    grit_defines += [
+      "-t",
+      "linux2",
+    ]
+  }
+  if (is_mac) {
+    grit_defines += [
+      "-t",
+      "darwin",
+    ]
+  }
+  if (is_win) {
+    grit_defines += [
+      "-t",
+      "win32",
+    ]
+  }
 }
 
 if (enable_extensions) {