Also statically link Boost for the 32-bit host

Somehow the Ubuntu 20.04 build just did this without being told, but the
Ubuntu 18.04 build did not. With the static link option Meson will by
default only search under /usr/lib, so for our CI builds we need to
explicitly tell it to also search under /usr/local/lib since that's
where we manually installed Boost 1.72.

meson.build

@@ -99,8 +99,12 @@ if get_option('use-bitbridge')
   # I honestly have no idea what the correct way to have `find_dependency()` use
   # `/usr/lib32` instead of `/usr/lib` is. If anyone does know, please tell me!
   winegcc = meson.get_compiler('cpp', native : false)
-  boost_dep = [winegcc.find_library('boost_filesystem')]
-  xcb_dep = [winegcc.find_library('xcb')]
+  boost_dep = winegcc.find_library(
+    'boost_filesystem',
+    static : true,
+    dirs : ['/usr/lib', '/usr/local/lib']
+  )
+  xcb_dep = winegcc.find_library('xcb')
 
   executable(
     host_name_32bit,