[gdb/testsuite] Fix infoline-reloc-main-from-zero.exp compilation

[gdb/testsuite] Fix infoline-reloc-main-from-zero.exp compilation

When running gdb.base/infoline-reloc-main-from-zero.exp, I see:
...
Running gdb/testsuite/gdb.base/infoline-reloc-main-from-zero.exp ...
gdb compile failed, ld: infoline-reloc-main-from-zero: \
  not enough room for program headers, try linking with -N
ld: final link failed: bad value
collect2: error: ld returned 1 exit status
UNTESTED: gdb.base/infoline-reloc-main-from-zero.exp: infoline-reloc-main-from-zero.exp
UNTESTED: gdb.base/infoline-reloc-main-from-zero.exp: failed to compile
...

Fix this by following the suggestion:
...
-set opts {debug "additional_flags=-nostdlib -emain -Wl,-Ttext=0x00"}
+set opts {debug "additional_flags=-nostdlib -emain -Wl,-Ttext=0x00 -Wl,-N"}
...

Tested on x86_64-linux.

gdb/testsuite/ChangeLog:

2019-07-24  Tom de Vries  <tdevries@suse.de>

	PR testsuite/24612
	* gdb.base/infoline-reloc-main-from-zero.exp: Add -Wl,-N to
	additional_flags.