make top-level .gitignore only apply to top-level files/directories (#1960)

SVN-Revision: 7728

.gitignore

@@ -1,8 +1,8 @@
-.config*
-bin
-build_*
-toolchain_build_*
-staging_dir_*
-tmp
-dl
-tool_build
+/.config*
+/bin
+/build_*
+/toolchain_build_*
+/staging_dir_*
+/tmp
+/dl
+/tool_build