libgomp GCN plugin: Clean up always-empty 'PLUGIN_GCN_CPPFLAGS', 'PLUGIN_GCN_LDFLAGS'
After recent commit
d6adba307508c75f1ccb2121eb1a43c9ab1d4056
"libgomp GCN plugin: Clean up unused references to system-provided HSA Runtime
library", these aren't set anymore.
libgomp/
* plugin/Makefrag.am (libgomp_plugin_gcn_la_CPPFLAGS): Don't
consider 'PLUGIN_GCN_CPPFLAGS'.
(libgomp_plugin_gcn_la_LDFLAGS): Don't consider
'PLUGIN_GCN_LDFLAGS'.
* plugin/configfrag.ac (PLUGIN_GCN_CPPFLAGS, PLUGIN_GCN_LDFLAGS):
Remove.
* Makefile.in: Regenerate.
* configure: Likewise.
* testsuite/Makefile.in: Likewise.
(cherry picked from commit
91a6dcd14915181b4bce51cd44b56a3e9f9d35d8)