Don't statically link Boost by default #20

Since this would only be needed for distribution, and we're already
doing something similar for libstdc++ on the Ubuntu 18.04 build. This
moves the static linking behind a new build option.

meson_options.txt

@@ -1,3 +1,6 @@
+# TODO: For the next major or minor release, deprecate these `use-*` flags and
+#       replace them with `with-*` variants.
+
 option(
   'use-bitbridge',
   type : 'boolean',
@@ -5,6 +8,13 @@ option(
   description : 'Build a 32-bit host application for hosting 32-bit plugins. See the readme for full instructions on how to use this.'
 )
 
+option(
+  'with-static-boost',
+  type : 'boolean',
+  value : false,
+  description : 'Enable static linking for Boost. Needed when distributing the binaries to other systems.'
+)
+
 option(
   'use-winedbg',
   type : 'boolean',