Specify INFO log severity for -XX:DumpGCPerformanceOnShutdown

The art script only has severity set to warning, this was causing
the GC timings to not get output.

Bug: 70630582
Test: art -Xmx512m -XX:DumpGCPerformanceOnShutdown .. some benchmark

Change-Id: I03e4e09836f0bd73fbbff3640b4db8617cc63c95
1 file changed