libssh2: Initial add

Signed-off-by: Jimmy Tang <jcftang@gmail.com>

Author: jcftang

pkgs/libssh2.yaml

@@ -0,0 +1,12 @@
+extends: [autotools_package]
+
+dependencies:
+  run: [pkg-config]
+
+sources:
+- key: tar.gz:5ldpqx457hns4y4gsbvgej7lftl3gjcx
+  url: http://www.libssh2.org/download/libssh2-1.4.3.tar.gz
+
+when_build_dependency:
+- prepend_path: PKG_CONFIG_PATH
+  value: '${ARTIFACT}/lib/pkgconfig'