fbcode_builder: getdeps: fboss: add OpenNSL fetcher

Summary:
This is towards getting open source FBOSS to build using fbcode_builder.
OpenNSL is one of the dependencies for FBOSS.

OpenNSL is github repository with headers and prebuilt opaque library. Thus, we
can't/don't need to build it. Thus, OpenNSL manifest uses NopBuilder.

fbcode_builder expects the library to be in installed/lib and headers to be in
installed/include, but OpenNSL lib structure is different.  Thus, add explicit
[install.fields] rule for bin/wedge => lib. Once a rule(s) is provided, we must
provide rule(s) for all, so add rule for include => include as well.

Reviewed By: wez

Differential Revision: D15593639

fbshipit-source-id: facb36ff7b9a31f5952ecbc1a9fdb834c0e68d11

build/fbcode_builder/manifests/OpenNSL

+[manifest]
+name = OpenNSL
+
+[download]
+url = https://github.com/Broadcom-Switch/OpenNSL/archive/v3.5.0.1.tar.gz
+sha256 = 00e5367a479c160aa273e4da4b978d5e38132324c8ea960cc1b142d048dad5f8
+
+[build]
+builder = nop
+subdir = OpenNSL-3.5.0.1
+
+[install.files]
+bin/wedge = lib
+include = include