coreutils: fix musl source bootstrap under some conditions

srcpkgs/coreutils/template

@@ -22,6 +22,11 @@ if [ "$CHROOT_READY" ]; then
 	fi
 fi
 
+if [ "$XBPS_TARGET_LIBC" = musl ]; then
+	export ac_cv_lib_error_at_line=no
+	export ac_cv_header_sys_cdefs_h=no
+fi
+
 alternatives="
  hostname:hostname:/usr/bin/hostname-coreutils
  hostname:hostname.1:/usr/share/man/man1/hostname-coreutils.1"