meson: add a couple missing networking dependencies

As evidenced in config.mak.uname and configure.ac, there are various
possible scenarios where these libraries are default-enabled in the
build, which mainly boils down to: SunOS. -lresolv is simply not the
only library that, when it exists, probably needs to be linked to for
networking.

Check for and add -lnsl -lsocket as well.

Signed-off-by: Eli Schwartz <eschwartz@gentoo.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: eli-schwartz

meson.build

@@ -1080,10 +1080,11 @@ if host_machine.system() == 'windows'
     networking_dependencies += winsock
   endif
 else
-  libresolv = compiler.find_library('resolv', required: false)
-  if libresolv.found()
-    networking_dependencies += libresolv
-  endif
+  networking_dependencies += [
+    compiler.find_library('nsl', required: false),
+    compiler.find_library('resolv', required: false),
+    compiler.find_library('socket', required: false),
+  ]
 endif
 libgit_dependencies += networking_dependencies