Explicitly add a .dockerignore rather than symlink

Alpine linux seems very confused by symlinks

.dockerignore

@@ -1 +0,0 @@
-.gitignore

.dockerignore

@@ -0,0 +1,23 @@
+.#*
+dist
+build
+*.tar.gz
+*.egg-info
+*.py[co]
+__pycache__
+MANIFEST
+
+.DS_Store
+.cache
+
+repo2docker/s2i
+
+^bin/
+lib/
+lib64/
+share/
+include/
+
+# Docs
+generated/
+test_file_text.txt

.gitignore

@@ -14,6 +14,7 @@ repo2docker/s2i
 
 ^bin/
 lib/
+lib64/
 share/
 include/