.gitignore: Add .envrc.

Change-Id: I65a78285f5c8480199815f53a7c89196edfb9526
diff --git a/.gitignore b/.gitignore
index af944aa..0506fc9 100644
--- a/.gitignore
+++ b/.gitignore
@@ -33,3 +33,6 @@
 # Gradle
 .gradle/
 build/
+
+# Shell
+.envrc