gtk-vnc: add indirect dependencies

Fixes:
Full linkage --cached --test --strict gtk-vnc output
  Indirect dependencies with linkage:
    at-spi2-core
    harfbuzz
    libx11
    pango

I took the opportunity to move the gettext build dep to the on_linux block:
- it's a build time dep on Linux
- it's a normal dep on macOS

Formula/g/gtk-vnc.rb

@@ -25,18 +25,21 @@ class GtkVnc < Formula
     sha256 x86_64_linux:   "9992fdf41743bef7fb279857b510441e0b95b63082ccaad5690a36776de48089"
   end
 
-  depends_on "gettext" => :build
   depends_on "gobject-introspection" => :build
   depends_on "meson" => :build
   depends_on "ninja" => :build
   depends_on "pkgconf" => :build
 
+  depends_on "at-spi2-core"
   depends_on "cairo"
   depends_on "gdk-pixbuf"
   depends_on "glib"
   depends_on "gnutls"
   depends_on "gtk+3"
+  depends_on "harfbuzz"
   depends_on "libgcrypt"
+  depends_on "libx11"
+  depends_on "pango"
 
   uses_from_macos "zlib"
 
@@ -45,7 +48,7 @@ class GtkVnc < Formula
   end
 
   on_linux do
-    depends_on "libx11"
+    depends_on "gettext" => :build
   end
 
   # coroutine: avoid ucontext impl on macOS M1 hardware. Remove in the next release