[source] automake: import upstream fix for perl 5.26

[LEDE Commits]

dangole pushed a commit to source.git, branch master:
https://git.lede-project.org/92c80f38cff3c20388f9ac13d5196f2745aeaf77

commit 92c80f38cff3c20388f9ac13d5196f2745aeaf77
Author: Daniel Golle <daniel at makrotopia.org>
AuthorDate: Wed Jun 7 19:39:33 2017 +0200

    automake: import upstream fix for perl 5.26
    
    Build broke as distributions now include Perl 5.26 and automake
    triggered an "Unescaped left brace in regex" error.
    Import upstream commit 13f00eb449 to fix that.
    
    Signed-off-by: Daniel Golle <daniel at makrotopia.org>
---
 .../010-automake-port-to-Perl-5.22-and-later.patch | 30 ++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/tools/automake/patches/010-automake-port-to-Perl-5.22-and-later.patch b/tools/automake/patches/010-automake-port-to-Perl-5.22-and-later.patch
new file mode 100644
index 0000000..31b9273
--- /dev/null
+++ b/tools/automake/patches/010-automake-port-to-Perl-5.22-and-later.patch
@@ -0,0 +1,30 @@
+From 13f00eb4493c217269b76614759e452d8302955e Mon Sep 17 00:00:00 2001
+From: Paul Eggert <eggert at cs.ucla.edu>
+Date: Thu, 31 Mar 2016 16:35:29 -0700
+Subject: [PATCH] automake: port to Perl 5.22 and later
+
+Without this change, Perl 5.22 complains "Unescaped left brace in
+regex is deprecated" and this is planned to become a hard error in
+Perl 5.26.  See:
+http://search.cpan.org/dist/perl-5.22.0/pod/perldelta.pod#A_literal_%22{%22_should_now_be_escaped_in_a_pattern
+* bin/automake.in (substitute_ac_subst_variables): Escape left brace.
+---
+ bin/automake.in | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/bin/automake.in b/bin/automake.in
+index a3a0aa318..2c8f31e14 100644
+--- a/bin/automake.in
++++ b/bin/automake.in
+@@ -3878,7 +3878,7 @@ sub substitute_ac_subst_variables_worker
+ sub substitute_ac_subst_variables
+ {
+   my ($text) = @_;
+-  $text =~ s/\${([^ \t=:+{}]+)}/substitute_ac_subst_variables_worker ($1)/ge;
++  $text =~ s/\$[{]([^ \t=:+{}]+)}/substitute_ac_subst_variables_worker ($1)/ge;
+   return $text;
+ }
+ 
+-- 
+2.13.1
+