ld testsuite fail with --disable-plugins

[Alan Modra]

	* testsuite/config/default.exp (dep_plug_opt): Don't set unless
	check_plugin_api_available returns true.

diff --git a/ld/testsuite/config/default.exp b/ld/testsuite/config/default.exp
index 66721ff618e..1d696811e8e 100644
--- a/ld/testsuite/config/default.exp
+++ b/ld/testsuite/config/default.exp
@@ -538,10 +538,11 @@ if { [check_compiler_available] } {
     }
 }
 
-if {[file exists .libs/libdep.so]} {
-  set dep_plug_opt "--plugin .libs/libdep.so"
-} elseif {[file exists .libs/libdep.dll]} {
-  set dep_plug_opt "--plugin .libs/libdep.dll"
-} else {
-    set dep_plug_opt ""
+set dep_plug_opt ""
+if [check_plugin_api_available] {
+    if {[file exists .libs/libdep.so]} {
+	set dep_plug_opt "--plugin .libs/libdep.so"
+    } elseif {[file exists .libs/libdep.dll]} {
+	set dep_plug_opt "--plugin .libs/libdep.dll"
+    }
 }

-- 
Alan Modra