x86/tools/relocs: Fix non-POSIX regexp

Trying to run a cross-compiled x86 relocs tool on a BSD based
HOSTCC leads to errors like

  VOFFSET arch/x86/boot/compressed/../voffset.h - due to: vmlinux
  CC      arch/x86/boot/compressed/misc.o - due to: arch/x86/boot/compressed/../voffset.h
  OBJCOPY arch/x86/boot/compressed/vmlinux.bin - due to: vmlinux
  RELOCS  arch/x86/boot/compressed/vmlinux.relocs - due to: vmlinux
empty (sub)expressionarch/x86/boot/compressed/Makefile:118: recipe for target 'arch/x86/boot/compressed/vmlinux.relocs' failed
make[3]: *** [arch/x86/boot/compressed/vmlinux.relocs] Error 1

It turns out that relocs.c uses patterns like

	"something(|_end)"

This is not valid syntax or gives undefined results according
to POSIX 9.5.3 ERE Grammar

	https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html

It seems to be silently accepted by the Linux regexp() implementation
while a BSD host complains.

Such patterns can be replaced by a transformation like

	"(|p1|p2)" -> "(p1|p2)?"

Fixes: fd952815 ("x86-32, relocs: Whitelist more symbols for ld bug workaround")
Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

arch/x86/tools/relocs.c

@@ -57,12 +57,12 @@ static const char * const sym_regex_kernel[S_NSYMTYPES] = {
 	[S_REL] =
 	"^(__init_(begin|end)|"
 	"__x86_cpu_dev_(start|end)|"
-	"(__parainstructions|__alt_instructions)(|_end)|"
-	"(__iommu_table|__apicdrivers|__smp_locks)(|_end)|"
+	"(__parainstructions|__alt_instructions)(_end)?|"
+	"(__iommu_table|__apicdrivers|__smp_locks)(_end)?|"
 	"__(start|end)_pci_.*|"
 	"__(start|end)_builtin_fw|"
-	"__(start|stop)___ksymtab(|_gpl)|"
-	"__(start|stop)___kcrctab(|_gpl)|"
+	"__(start|stop)___ksymtab(_gpl)?|"
+	"__(start|stop)___kcrctab(_gpl)?|"
 	"__(start|stop)___param|"
 	"__(start|stop)___modver|"
 	"__(start|stop)___bug_table|"