meson: Omit .vapi from publicly visible dependency

So that consuming projects don't need a Vala compiler to use us as a
subproject.

src/api/generate.py

@@ -9,7 +9,7 @@
 
 def main():
     parser = argparse.ArgumentParser(description="Generate refined Frida API definitions")
-    parser.add_argument('--output', dest='output_type', choices=['bundle', 'header', 'vapi'], default='bundle')
+    parser.add_argument('--output', dest='output_type', choices=['bundle', 'header', 'vapi', 'vapi-stamp'], default='bundle')
     parser.add_argument('api_version', metavar='api-version', type=str)
     parser.add_argument('core_vapi', metavar='/path/to/frida-core.vapi', type=argparse.FileType('r', encoding='utf-8'))
     parser.add_argument('core_header', metavar='/path/to/frida-core.h', type=argparse.FileType('r', encoding='utf-8'))
@@ -19,13 +19,18 @@ def main():
 
     args = parser.parse_args()
 
+    output_type = args.output_type
     api_version = args.api_version
     core_vapi = args.core_vapi.read()
     core_header = args.core_header.read()
     base_vapi = args.base_vapi.read()
     base_header = args.base_header.read()
     output_dir = Path(args.output_dir)
 
+    if output_type == 'vapi-stamp':
+        (output_dir / f"frida-core-{api_version}.vapi.stamp").write_bytes(b"")
+        return
+
     toplevel_names = [
         "frida.vala",
         "control-service.vala",
@@ -42,7 +47,6 @@ def main():
 
     enable_header = False
     enable_vapi = False
-    output_type = args.output_type
     if output_type == 'bundle':
         enable_header = True
         enable_vapi = True

src/api/meson.build

@@ -36,6 +36,16 @@ core_public_vapi = custom_target('frida-core-vapi',
   install_dir: get_option('datadir') / 'vala' / 'vapi',
 )
 
+core_public_vapi_stamp =  custom_target('frida-core-vapi-stamp',
+  input: core_public_vapi,
+  output: f'frida-core-@[email protected]',
+  command: [
+    generate_api,
+    '--output=vapi-stamp',
+    generate_api_args,
+  ],
+)
+
 core_public_lib = custom_target('frida-core-library',
   input: [core] + internal_libs,
   output: f'libfrida-core-@[email protected]',
@@ -61,7 +71,7 @@ if host_os == 'android'
 endif
 
 core_public_dep = declare_dependency(
-  sources: [core_public_h, core_public_vapi] + core_public_extra_headers,
+  sources: [core_public_h, core_public_vapi_stamp, core_public_extra_headers],
   include_directories: include_directories('.'),
   link_args: backend_libs_private,
   link_with: core_public_lib,