fix usage of broken feature in meson.build file

It seems that we are trying to convert file objects to strings which is
considered as a misfeature since it does not work reliably.

This is the warning that is seen while building pldm:

``` WARNING: Broken features used:
 * 1.3.0: {'str.format: Value other than strings, integers, bools, options,
   dictionaries and lists thereof.'}
```

Tested:

Rebuild pldm repository with the fix and it builds pldm without the
mentioned warning above.

Change-Id: If8fedf488d33de6dccc2c1b45c2bfe124fbc3384
Signed-off-by: Manojkiran Eda <manojkiran.eda@gmail.com>
diff --git a/meson.build b/meson.build
index 1336ba8..6f96291 100644
--- a/meson.build
+++ b/meson.build
@@ -69,11 +69,12 @@
 elif get_option('transport-implementation') == 'af-mctp'
   conf_data.set('PLDM_TRANSPORT_WITH_AF_MCTP', 1)
 endif
-config = configure_file(output: 'config.h',
+
+configure_file(output: 'config.h',
   configuration: conf_data
 )
 
-add_project_arguments('-include', '@0@'.format(config), language: 'cpp')
+add_project_arguments('-include', '@0@'.format(meson.current_build_dir() /'config.h'), language: 'cpp')
 
 filesystem = import('fs')