Fix meson.build to work properly with '-Ddatabase=false'

NEWS

@@ -4,6 +4,7 @@ ver 0.21.8 (not yet released)
   - httpd: fix use-after-free bug
 * fix Bonjour bug
 * fix build failure with GCC 9
+* fix build failure with -Ddatabase=false
 * systemd: add user socket unit
 
 ver 0.21.7 (2019/04/03)

meson.build

@@ -367,8 +367,10 @@ basic_dep = declare_dependency(
 
 if enable_database
   subdir('src/storage')
-  subdir('src/db')
+else
+  storage_glue_dep = dependency('', required: false)
 endif
+subdir('src/db')
 
 if neighbor_glue_dep.found()
   sources += 'src/command/NeighborCommands.cxx'

src/db/meson.build

@@ -9,6 +9,11 @@ db_api_dep = declare_dependency(
   link_with: db_api,
 )
 
+if not enable_database
+  db_glue_dep = db_api_dep
+  subdir_done()
+endif
+
 subdir('plugins')
 
 db_glue_sources = [