Add build rules for statically linked oatdump on host.

Also extend oatdump_test to exercise oatdump(d)s.

Test: ART_BUILD_HOST_STATIC=true m test-art-host-gtest-oatdump_test
Bug: 29530992
Change-Id: I6eb6c96f385832733d18d0400abd9974a6d8e45c
diff --git a/build/art.go b/build/art.go
index 4e64dcf..f305c07 100644
--- a/build/art.go
+++ b/build/art.go
@@ -67,6 +67,12 @@
 		cflags = append(cflags, "-fstack-protector")
 	}
 
+	// Are additional statically-linked ART host binaries
+	// (dex2oats, oatdumps, etc.) getting built?
+	if envTrue(ctx, "ART_BUILD_HOST_STATIC") {
+		cflags = append(cflags, "-DART_BUILD_HOST_STATIC=1")
+	}
+
 	return cflags, asflags
 }