Add .gitignore for package.xml file generated by SDK Manager

Bug: 233804920
Test: git status
Change-Id: Icfb92e032d29266c915d54296ac3b541ff53bfe6
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..f1e25bb
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+package.xml