Use LIBRSVG_LIBS, LIBM to satisfy dependencies of RUST_LIB

Otherwise linking with -Wl,--as-needed fails.

Signed-off-by: Simon McVittie <smcv@debian.org>
3 jobs for link-order in 8 minutes and 2 seconds (queued for 14 minutes and 14 seconds)
Status Job ID Name Coverage
  Test
passed #93214
fedora test

00:07:37

 
  Lint
manual #93216
allowed to fail manual
clippy
passed #93215
rustfmt

00:00:24