[R-pkg-team] Bug#1104454: r-cran-bslib: test fail - Undefined variable: "$transition-collapse-width"

[Rebecca N. Palmer]

Control: tags -1 patch

It passes on Salsa (i.e. after rebuilding the package) but fails on 
debci.  It looks like the reason is that this package uses a patched 
_variables.scss created at build time, but a link to _transitions.scss, 
so it's seeing the build-time (libjs-bootstrap4 4.6.1) _variables.scss 
but the test-time (4.6.2) _transitions.scss.

The immediate fix is hence to no-change rebuild it (it's arch:all so 
that will need to be a sourceful upload, not a binNMU).

In the longer term, we probably also want a mechanism to remind us to do 
that if libjs-bootstrap4 is updated; I vaguely remember there being a 
static linking register for that purpose.