I was having the same issue with Robotium and the lint markers. Instead of modifying any manifest files, I suggest disabling the minSDK lint check for your project that is using Robotium.
"Clear Lint Markers" removed the error temporarily, but it kept coming back every time I saved a file in the affected project.
Here's what worked for me:
Right click project -> Properties -> Android Lint Preferences
Search for "minSdk" in the search box
Click on "UsesMinSdkAttributes"
Click the "Ignore All" button at the bottom. Clean and rebuild the project, and Eclipse/ADT will no longer run the lint check for minSdk on your project.