meson: Force inclusion of config.h via `-include`

Make sure there's no ambiguity about which config.h is used for includes
in the event that libpldm acquires subprojects, or is used as a
subproject itself.

Tested: `meson compile -C build` succeeds

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: I08c3bdc807cc268d2401e06f0bfaee07f89ba534
diff --git a/meson.build b/meson.build
index 0f8fa91..9e2096b 100644
--- a/meson.build
+++ b/meson.build
@@ -36,6 +36,12 @@
   conf.set('LIBPLDM_ABI_TESTING', '')
 endif
 
+config = configure_file(output: 'config.h',
+  configuration: conf
+)
+
+add_project_arguments('-include', '@0@'.format(config), language: 'c')
+
 libpldm_sources = files()
 subdir('src')
 
@@ -75,10 +81,6 @@
   version: meson.project_version(),
   libraries: libpldm)
 
-configure_file(output: 'config.h',
-  configuration: conf
-)
-
 if get_option('tests').enabled()
   subdir('tests')