make gitignore happy with symlinks

See https://codereview.chromium.org/139473002 for similar CL.

R=djsollen@google.com, mtklein@google.com

Author: halcanary@google.com

Review URL: https://codereview.chromium.org/267543002

git-svn-id: http://skia.googlecode.com/svn/trunk@14484 2bbb7eff-a529-9590-31e7-b0007b416f81

platform_tools/android/.gitignore

@@ -1,11 +1,11 @@
-/third_party/externals/
-/toolchains/
+third_party/externals
+toolchains
 .cproject
-.externalToolBuilders/
+.externalToolBuilders
 .project
 .pydevproject
 app/.classpath
 app/.project
-app/bin/
-app/gen/
+app/bin
+app/gen
 app/lint.xml