build: add libsysprof-capture-2 static library

This allows external tooling to write capture files that Sysprof can open.
Ideally, this will get used by GJS in the near future to implement profiler
output for Sysprof.

tests/meson.build

@@ -8,7 +8,7 @@ test_env = [
 
 test_capture = executable('test-capture',
   'test-capture.c',
-  dependencies: libsysprof_dep,
+  dependencies: libsysprof_capture_dep,
 )
 test('test-capture', test_capture, env: test_env)