Add host Art 12.0.0-beta4

Test: tools/test.py --no-internal --runtimes=dex-12.0.0
Bug: 197077780
Change-Id: I963f8d3c44ed73969420afe6a7e28a64d3a753ba
diff --git a/.gitignore b/.gitignore
index 80c9662..07f90a7 100644
--- a/.gitignore
+++ b/.gitignore
@@ -262,6 +262,8 @@
 tools/*/art-9.0.0.tar.gz
 tools/*/art-10.0.0
 tools/*/art-10.0.0.tar.gz
+tools/*/host/art-12.0.0-beta4
+tools/*/host/art-12.0.0-beta4.tar.gz
 tools/*/art.tar.gz
 tools/*/dalvik
 tools/*/dalvik-4.0.4