strip ANSI sequences from docker build output

sharness was failing because an ANSI reset sequence was getting inserted at the
beginning of the line.

License: MIT
Signed-off-by: Steven Allen <steven@stebalien.com>

test/ipfs-test-lib.sh

@@ -1,5 +1,9 @@
 # Generic test functions for go-ipfs
 
+ansi_strip() {
+    sed 's/\x1b\[[0-9;]*m//g'
+}
+
 # Quote arguments for sh eval
 shellquote() {
 	_space=''
@@ -48,7 +52,7 @@ test_path_cmp() {
 
 # This takes a Dockerfile, and a build context directory
 docker_build() {
-    docker build --rm -f "$1" "$2"
+    docker build --rm -f "$1" "$2" | ansi_strip
 }
 
 # This takes an image as argument and writes a docker ID on stdout