have import-maven-artifacts.sh ignore missing dirs

Change-Id: I2412ebba80ad9ddda01ab64701d69acbede40a9c
diff --git a/import-maven-artifacts.sh b/import-maven-artifacts.sh
index b2f8101..2d15242 100755
--- a/import-maven-artifacts.sh
+++ b/import-maven-artifacts.sh
@@ -123,8 +123,10 @@
 function announceCopy() {
   input=$1
   output=$2
-  echo copying "$input" to "$output"
-  cp -rT $input $output
+  if stat $input > /dev/null 2>/dev/null; then
+    echo copying "$input" to "$output"
+    cp -rT $input $output
+  fi
 }
 
 function export() {