libssh: fix build with musl libc

libssh uses GNU extensions to the glob() API. Update the cmake test to
take that into account so that glob() is not used with musl libc.

Fixes:
http://autobuild.buildroot.net/results/0c2/0c2d17316fd6bd2bf1359e23a2a1273fa349cf2a/
http://autobuild.buildroot.net/results/936/936abac5362b33980fd1efe8b830409ee2f86f6b/
http://autobuild.buildroot.net/results/51b/51b1b136ab4209ee443c1b450a932341b2ff81b7/

Cc: Scott Fan <fancp2007@gmail.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/libssh/0001-cmake-check-for-GNU-compatible-glob-support.patch

@@ -0,0 +1,44 @@
+From 3bb8b5e4517a720d178dbe5c53b4a444d718bcf1 Mon Sep 17 00:00:00 2001
+From: Baruch Siach <baruch@tkos.co.il>
+Date: Fri, 14 Sep 2018 15:19:48 +0300
+Subject: [PATCH] cmake: check for GNU compatible glob support
+
+The GLOB_TILDE flag is a GNU extension. musl libc does not implement
+this extension, which leads to build failure:
+
+.../libssh-0.8.1/src/config.c: In function 'local_parse_glob':
+/home/buildroot/autobuild/run/instance-1/output/build/libssh-0.8.1/src/config.c:329:10: error: 'glob_t {aka struct <anonymous>}' has no member named 'gl_flags'; did you mean 'gl_offs'?
+         .gl_flags = 0,
+          ^~~~~~~~
+          gl_offs
+.../libssh-0.8.1/src/config.c:334:25: error: 'GLOB_TILDE' undeclared (first use in this function); did you mean '_IO_FILE'?
+     rt = glob(fileglob, GLOB_TILDE, NULL, &globbuf);
+                         ^~~~~~~~~~
+                         _IO_FILE
+
+Check for GLOB_TILDE directly to make sure the libc provides the
+required extension.
+
+Signed-off-by: Baruch Siach <baruch@tkos.co.il>
+---
+Upstream status: https://www.libssh.org/archive/libssh/2018-09/0000020.html
+
+ ConfigureChecks.cmake | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/ConfigureChecks.cmake b/ConfigureChecks.cmake
+index f91bd038f5a3..dac61bcf678e 100644
+--- a/ConfigureChecks.cmake
++++ b/ConfigureChecks.cmake
+@@ -156,7 +156,7 @@ check_function_exists(explicit_bzero HAVE_EXPLICIT_BZERO)
+ check_function_exists(memset_s HAVE_MEMSET_S)
+ 
+ if (HAVE_GLOB_H)
+-  check_function_exists(glob HAVE_GLOB)
++  check_symbol_exists(GLOB_TILDE "glob.h" HAVE_GLOB)
+ endif (HAVE_GLOB_H)
+ 
+ if (NOT WIN32)
+-- 
+2.18.0
+