Add gitignore

Signed-off-by: Alessandro Comodi <acomodi@antmicro.com>

.gitignore

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..fa2f6f2
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+build/
+env/