8261758: [TESTBUG] gc/g1/TestGCLogMessages.java fails if ergonomics detect too small InitialHeapSize

Reviewed-by: tschatzl, sjohanss

test/hotspot/jtreg/gc/g1/TestGCLogMessages.java

@@ -260,6 +260,7 @@ public class TestGCLogMessages {
         pb = ProcessTools.createJavaProcessBuilder("-XX:+UseG1GC",
                                                    "-Xmx32M",
                                                    "-Xmn16M",
+                                                   "-Xms32M",
                                                    "-Xlog:gc+phases=trace",
                                                    GCTestWithEvacuationFailure.class.getName());