Make build.sh work for windows plugins.

When building the windows plugin exe's (host-local, flannel, win-overlay, win-bridge),
it was necessary to use 'GOOS=windows go build path/to/plugin' rather than the build script.

This makes 'GOOS=windows GOARCH=amd64 ./build.sh' build all the windows plugin binaries.

build.sh

@@ -20,19 +20,28 @@ export GO="${GO:-go}"
 mkdir -p "${PWD}/bin"
 
 echo "Building plugins ${GOOS}"
+if [[ $GOOS == "windows" ]]; then
+  PLUGINS=$(cat plugins/windows_only.txt)
+  if [ "$GOARCH" == "amd64" ]; then
+    for d in $PLUGINS; do
+      if [ -d "$d" ]; then
+        plugin="$(basename "$d").exe"
+	echo "  $plugin"
+	$GO build -o "${PWD}/bin/$plugin" "$@" "$REPO_PATH"/$d
+      fi
+    done
+  else
+    echo "Could not build windows plugins when GOARCH != amd64"
+  fi
+else
   PLUGINS="plugins/meta/* plugins/main/* plugins/ipam/* plugins/sample"
   for d in $PLUGINS; do
 	  if [ -d "$d" ]; then
 		  plugin="$(basename "$d")"
-		if [ $plugin == "windows" ]
+		  if [ $plugin != "windows" ]; then
-		then
-			if [ "$GOARCH" == "amd64" ]
-			then
-				GOOS=windows . $d/build.sh
-			fi
-		else
 			  echo "  $plugin"
 		          $GO build -o "${PWD}/bin/$plugin" "$@" "$REPO_PATH"/$d
 		  fi
 	  fi
   done
+fi