sim: testsuite: replace global_ld_options with LDFLAGS_FOR_TARGET

Only a few tests actually use global_ld_options, but we can replace the
sim-specific settings with the dejagnu common LDFLAGS_FOR_TARGET and get
the same result.

sim/testsuite/example-synacor/allinsn.exp

@@ -4,7 +4,8 @@ if [istarget *] {
     # All machines.
     set all_machs "example"
 
-    set global_ld_options "-Ttext=0"
+    global LDFLAGS_FOR_TARGET
+    set LDFLAGS_FOR_TARGET "-Ttext=0"
 
     foreach src [lsort [glob -nocomplain $srcdir/$subdir/*.s]] {
 	# If we're only testing specific files and this isn't one of them,
@@ -15,5 +16,5 @@ if [istarget *] {
 	run_sim_test $src $all_machs
     }
 
-    unset global_ld_options
+    unset LDFLAGS_FOR_TARGET
 }