fix: ignore built artifacts in third_party submodules

Signed-off-by: Sam Gammon <sam@elide.dev>

Author: sgammon

.gitmodules

@@ -12,6 +12,9 @@
 [submodule "apr"]
 	path = third_party/apache/apr
 	url = git@github.com:apache/apr.git
+	ignore = dirty
 [submodule "boringssl"]
 	path = third_party/google/boringssl
 	url = git@github.com:google/boringssl.git
+	ignore = dirty
+