scripts/setup-env.sh: Set prompt when sourced
scripts/setup-env.sh: Set prompt when sourced

When sourced,

  shenki@icarus ~/dev/foo/HDMI2USB-misoc-firmware $

becomes:

  (HDMI2USB)shenki@icarus ~/dev/foo/HDMI2USB-misoc-firmware $

Signed-off-by: Joel Stanley <4816dabf8db1bc6cac35b3a24cab2ff844b5b0c7@jms.id.au>

mithro/HDMI2USB-litex-firmware,mithro/HDMI2USB-litex-firmware,cr1901/HDMI2USB-litex-firmware,cr1901/HDMI2USB-litex-firmware,mithro/HDMI2USB-litex-firmware,mithro/HDMI2USB-litex-firmware,cr1901/HDMI2USB-litex-firmware,cr1901/HDMI2USB-litex-firmware