fix quotes in extdir variable

src/meson.build

@@ -1,7 +1,7 @@
 configure_file(output: 'config.h', configuration: conf)
 
 gresource_sources = include_directories('gresource')
-extdir = '"@0@/@1@"'.format(get_option('libdir'), 'lightdm-webkit2-greeter')
+extdir = '@0@/@1@'.format(get_option('libdir'), 'lightdm-webkit2-greeter')
 
 # ======================================= #
 # ------->>> Webkit2 Extension <<<------- #
@@ -26,7 +26,7 @@ webext = shared_library(
 greeter_sources = ['gresource/greeter-resources.c', 'greeter.c']
 
 greeter_cargs = [
-    '-DLIGHTDM_WEBKIT2_GREETER_EXTENSIONS_DIR=@0@'.format(extdir)
+    '-DLIGHTDM_WEBKIT2_GREETER_EXTENSIONS_DIR="@0@"'.format(extdir)
 ]
 
 greeter = executable(