When emit_lib_vt is set, the dist tarball is now named
ghostty-vt-<version>.tar.gz and excludes large files that are
unnecessary for building libghostty-vt. This reduces the archive
from ~36MB to ~2.8MB by excluding images, macOS app resources,
font assets, fuzz test corpus, crash testdata, and vendored
libraries not used by lib-vt.
GTK resources and frame data generation are also skipped since
lib-vt does not need them, which removes the GTK build-time
dependency. The distcheck step runs test-lib-vt instead of the
full test suite for lib-vt archives.
7a59e966b8