build: add a SlackBuild under assets/slackbuild

Packages the application for Slackware, following SBo conventions with
two deliberate departures: the tag is _danix rather than _SBo and the
package type is txz rather than tgz, since this is not an SBo
submission. sbolint reports exactly those two as errors and nothing
else; the template comments it warned about are gone.

Written against the install layout the build really produces, checked by
staging it: one binary, one .desktop entry and one scalable icon, no
libraries and no man or info pages. The template's .la removal, man and
info compression and perllocal.pod cleanup would all act on nothing
here, so they are left out rather than carried along as dead code.
doinst.sh keeps only the desktop-database and icon-cache updates.

The download URL and checksum are verified rather than assumed: sbodl
fetches the tarball and reports "md5sum matches OK".

Adds QTMAILDIR_BUILD_TESTS, defaulting to ON so the ordinary build is
unchanged. A packaging build has no use for the test binaries, and
building them pulls in Qt6::Test to produce nothing that ships. Note the
0.4.0 tarball predates this option, so with that source the flag is
accepted but does nothing; the README says so.

notmuch is the only dependency outside Slackware. Qt6 including
WebEngine, gmime and cmake are all stock, which is what REQUIRES
reflects.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/assets/slackbuild/slack-desc b/assets/slackbuild/slack-desc
new file mode 100644
index 0000000..e4292cd
--- /dev/null
+++ b/assets/slackbuild/slack-desc
@@ -0,0 +1,19 @@
+# HOW TO EDIT THIS FILE:
+# The "handy ruler" below makes it easier to edit a package description.
+# Line up the first '|' above the ':' following the base package name, and
+# the '|' on the right side marks the last column you can put a character in.
+# You must make exactly 11 lines for the formatting to be correct.  It's also
+# customary to leave one space after the ':' except on otherwise blank lines.
+
+         |-----handy-ruler------------------------------------------------------|
+qtmaildir: qtmaildir (Qt6 mail client for notmuch-indexed Maildirs)
+qtmaildir:
+qtmaildir: A desktop client for reading and organizing a local Maildir that
+qtmaildir: notmuch has indexed. A GUI counterpart to neomutt for the parts of
+qtmaildir: mail handling that are easier with a mouse and a real HTML renderer.
+qtmaildir:
+qtmaildir: It does no network protocol work at all: no POP, IMAP or SMTP.
+qtmaildir: Mail arrives by whatever you already use and is indexed by
+qtmaildir: 'notmuch new'. Fetching is delegated to a command you configure.
+qtmaildir:
+qtmaildir: Homepage: https://git.danix.xyz/qtmaildir