GCC, GDB, and binutils have mainline support for msp430-elf target.
There's, afaict, a "GDB server" kind of tool which works with many debuggers: http://dlbeer.co.nz/mspdebug/
TI has some info on their packaging of the toolchain and related software which is very confusing in terms of version numbers: http://software-dl.ti.com/msp430/msp430_public_sw/mcu/msp430/MSPGCC/latest/index_FDS.html
Debian seems to only have quite old gcc-msp430 and binutils-msp430 and msp430mcu (linker scripts, headers, etc) packages from 2011 and 2012. Would be nice to get updates to these with mainline code.