[meson] Use the recommended way to generate harfbuzz.cc

As https://github.com/harfbuzz/harfbuzz/pull/2532

src/gen-harfbuzzcc.py

@@ -1,22 +1,18 @@
 #!/usr/bin/env python3
 
-"usage: gen-harfbuzzcc.py harfbuzz.cc hb-blob.cc hb-buffer.cc ..."
+"This tool is intended to be used from meson"
 
-import os, sys
-
-os.chdir (os.path.dirname (__file__))
+import os, sys, shutil
 
 if len (sys.argv) < 3:
-	sys.exit (__doc__)
+	exit (__doc__)
 
-output_file = sys.argv[1]
-source_paths = sys.argv[2:]
+OUTPUT = sys.argv[1]
+CURRENT_SOURCE_DIR = sys.argv[2]
+sources = sys.argv[3:]
 
-result = "".join ('#include "{}"\n'.format (os.path.basename (x)) for x in source_paths if x.endswith (".cc")).encode ()
+with open (OUTPUT, "wb") as f:
+	f.write ("".join ('#include "{}"\n'.format (os.path.basename (x)) for x in sources if x.endswith (".cc")).encode ())
 
-with open (output_file, "rb") as f:
-	current = f.read()
-
-if result != current:
-	with open (output_file, "wb") as f:
-		f.write (result)
+# copy it also to src/
+shutil.copyfile (OUTPUT, os.path.join (CURRENT_SOURCE_DIR, os.path.basename (OUTPUT)))

src/meson.build

@@ -301,9 +301,7 @@ else
       input: rl,
       output: hh,
       command: [find_program('gen-ragel-artifacts.py'),
-                '@OUTPUT@',
-                '@CURRENT_SOURCE_DIR@',
-                '@INPUT@'],
+                '@OUTPUT@', '@CURRENT_SOURCE_DIR@', '@INPUT@'],
     )
   endforeach
 endif
@@ -311,10 +309,12 @@ endif
 custom_target('harfbuzz.cc',
   build_by_default: true,
   output: 'harfbuzz.cc',
-  command: [find_program('gen-harfbuzzcc.py'), 'harfbuzz.cc'] +
-            hb_base_sources + hb_glib_sources + hb_ft_sources +
+  input: hb_base_sources + hb_glib_sources + hb_ft_sources +
          hb_graphite2_sources + hb_uniscribe_sources + hb_gdi_sources +
-            hb_directwrite_sources + hb_coretext_sources)
+         hb_directwrite_sources + hb_coretext_sources,
+  command: [find_program('gen-harfbuzzcc.py'),
+            '@OUTPUT@', '@CURRENT_SOURCE_DIR@', '@INPUT@'],
+)
 
 incsrc = include_directories('.')