[gdb/testsuite] Fix re-used exec in gdb.arch/ftrace-insn-reloc.exp

In test-case gdb.arch/ftrace-insn-reloc.exp we generate two executables with
the same name, which is confusing and known to cause trouble.

Fix this by making the executable names unique.

Tested on x86_64-linux.

gdb/testsuite/gdb.arch/ftrace-insn-reloc.exp

@@ -15,13 +15,11 @@
 load_lib "trace-support.exp"
 
 standard_testfile insn-reloc.c
-set executable $testfile
-set expfile $testfile.exp
 
 # Some targets have leading underscores on assembly symbols.
 set additional_flags [gdb_target_symbol_prefix_flags]
 
-if [prepare_for_testing "failed to prepare" $executable $srcfile \
+if [prepare_for_testing "failed to prepare" $testfile-no-ipa $srcfile \
 	[list debug $additional_flags]] {
     return -1
 }
@@ -47,7 +45,7 @@ if { [gdb_compile "$srcdir/$subdir/$srcfile" $binfile \
     untested "failed to compile"
     return -1
 }
-clean_restart ${executable}
+clean_restart $testfile
 
 if ![runto_main] {
     return 0