fix(unity): GridFire supports unity builds

GridFire can now support unity builds. This is useful for python
bindings. The main limitation is that openssl (a dependency of
libplugin) does not support unity builds. Therefore when building in a
unity build libplugin must be disabled. This is done with the
-Dunity-safe=ture flag at setup time

build-config/fourdst/meson.build

@@ -1,9 +1,17 @@
 # bring in all of the fourdst utility repositories
 
+fourdst_build_lib_all = true
+if get_option('unity-safe')
+    fourdst_build_lib_all=false
+endif
+
 fourdst_sp = subproject('fourdst',
                         default_options:
                             ['build-tests=' + get_option('build-tests').to_string(),
-                             'build-python=' + get_option('build-python').to_string()
+                             'build-python=' + get_option('build-python').to_string(),
+                             'build-lib-all=' + fourdst_build_lib_all.to_string(),
+                             'pkg-config=' + get_option('pkg-config').to_string(),
+                             'build-lib-log=true'
                             ]
 )
 
@@ -11,10 +19,15 @@ composition_dep = fourdst_sp.get_variable('composition_dep')
 log_dep = fourdst_sp.get_variable('log_dep')
 const_dep = fourdst_sp.get_variable('const_dep')
 config_dep = fourdst_sp.get_variable('config_dep')
-plugin_dep = fourdst_sp.get_variable('plugin_dep')
+if not get_option('unity-safe')
+    plugin_dep = fourdst_sp.get_variable('plugin_dep')
+endif
 
 libcomposition = fourdst_sp.get_variable('libcomposition')
 libconst = fourdst_sp.get_variable('libconst')
 libconfig = fourdst_sp.get_variable('libconfig')
 liblogging = fourdst_sp.get_variable('liblogging')
-libplugin = fourdst_sp.get_variable('libplugin')
+
+if not get_option('unity-safe')
+    libplugin = fourdst_sp.get_variable('libplugin')
+endif