We're seeing crashes on SPARC in g1ParScanThreadState. These seemed to start,
or at least get worse, with the following fix.
8250597: G1: Improve inlining around trim_queue
https://bugs.openjdk.org/browse/JDK-8250597
Most of that was shuffling code around, but also added ATTRIBUTE_FLATTEN
We disable it on SPARC, which seems to help, and if we do get a crash we
will get a better stack trace.

--- a/src/hotspot/share/utilities/globalDefinitions_gcc.hpp	Wed Dec  4 13:28:49 2024
+++ b/src/hotspot/share/utilities/globalDefinitions_gcc.hpp	Mon Jan 20 09:22:43 2025
@@ -259,7 +259,9 @@
 // Inlining support
 #define NOINLINE     __attribute__ ((noinline))
 #define ALWAYSINLINE inline __attribute__ ((always_inline))
+#ifndef SPARC
 #define ATTRIBUTE_FLATTEN __attribute__ ((flatten))
+#endif
 
 // Alignment
 //