[build] generate hb-version.h once at configure time with Meson

Currently with Meson hb-version.h is generated during the build without
any explicit dependencies which can result in build failures due races
over the file.

Change this to be generated at configure time, so that the file is always
generated once before the build itself.

Closes #2667

src/meson.build

@@ -1,3 +1,10 @@
+hb_version_h = configure_file(
+               command: [find_program('gen-hb-version.py'), meson.project_version(), '@OUTPUT@', '@INPUT@'],
+               input: 'hb-version.h.in',
+               output: 'hb-version.h',
+               install: true,
+               install_dir: join_paths(get_option('includedir'), meson.project_name()))
+
 # Base and default-included sources and headers
 hb_base_sources = files(
   'hb-aat-layout-ankr-table.hh',
@@ -214,9 +221,9 @@ hb_base_headers = files(
   'hb-shape.h',
   'hb-style.h',
   'hb-unicode.h',
-  'hb-version.h',
   'hb.h',
 )
+hb_base_headers += hb_version_h
 
 # Optional Sources and Headers with external deps
 
@@ -281,14 +288,6 @@ hb_gobject_headers = files(
   'hb-gobject-structs.h',
 )
 
-custom_target('hb-version.h',
-  build_by_default: true,
-  input: 'hb-version.h.in',
-  output: 'hb-version.h',
-  command: [find_program('gen-hb-version.py'), meson.project_version(),
-            '@OUTPUT@', '@INPUT@'],
-)
-
 ragel = find_program('ragel', required: false)
 if not ragel.found()
   warning('You have to install ragel if you are going to develop HarfBuzz itself')