Fix some minor bugs for droiddoc

1) typo: check-api -> checkapi
2) newlines in the error messages are correctly emitted

Bug: 77575606
Bug: 78034256
Test: m -j checkapi

Change-Id: Ibeef4d9f4f7f2ca48c29c23b1784efa6aa53a364
diff --git a/java/androidmk.go b/java/androidmk.go
index 5a4a082..88dc6ef 100644
--- a/java/androidmk.go
+++ b/java/androidmk.go
@@ -292,7 +292,7 @@
 						ddoc.checkCurrentApiTimestamp.String())
 
 					fmt.Fprintln(w, ".PHONY: checkapi")
-					fmt.Fprintln(w, "check-api:",
+					fmt.Fprintln(w, "checkapi:",
 						ddoc.checkCurrentApiTimestamp.String())
 
 					fmt.Fprintln(w, ".PHONY: droidcore")