Needed to fix build on ppc + musl. Should pop up in next gnulib sync in release (different patch).

https://www.openwall.com/lists/musl/2017/11/05/2
https://github.com/void-linux/void-packages/blob/master/srcpkgs/grep/patches/ppc-musl.patch
https://git.savannah.gnu.org/cgit/gnulib.git/commit/?id=2d830e4a792fcd9f614ed08a7f18584b8b21d23b
--- a/lib/sigsegv.c
+++ b/lib/sigsegv.c
@@ -221,8 +221,10 @@ int libsigsegv_version = LIBSIGSEGV_VERSION;
 /* both should be equivalent */
 #   if 0
 #    define SIGSEGV_FAULT_STACKPOINTER  ((ucontext_t *) ucp)->uc_mcontext.regs->gpr[1]
-#   else
+#   elif defined(__GLIBC__)
 #    define SIGSEGV_FAULT_STACKPOINTER  ((ucontext_t *) ucp)->uc_mcontext.uc_regs->gregs[1]
+#   else
+#    define SIGSEGV_FAULT_STACKPOINTER  ((ucontext_t *) ucp)->uc_mcontext.gregs[1]
 #   endif
 #  endif