Bash doesn't like sourcing a filename with a tilde in it

[rwhitby]

Fixes #15.

Before:

rwhitby@win11:~/Projects/kintex-chatter/xc7k325t-blinky-nextpnr$ make BOARD=qmtech
/bin/bash: ~/opt/prjxray/utils/environment.sh: No such file or directory
make: *** [Makefile:34: blinky.frames] Error 1

After (I temporarily removed the @ so you could see the path resolved):

rwhitby@win11:~/Projects/kintex-chatter/xc7k325t-blinky-nextpnr$ make BOARD=qmtech
. "/home/rwhitby/opt/prjxray/utils/environment.sh"
fasm2frames --part xc7k325tffg676-1 --db-root /home/rwhitby/opt/nextpnr/prjxray-db/kintex7 blinky.fasm > blinky.frames
xc7frames2bit --part_file /home/rwhitby/opt/nextpnr/prjxray-db/kintex7/xc7k325tffg676-1/part.yaml --part_name xc7k325tffg676-1 --frm_file blinky.frames --output_file blinky.bit

[unbtorsten]

Can you adjust the submodule path from git@github.com:rwhitby/nextpnr-xilinx.git to git@github.com:kintex-chatter/nextpnr-xilinx.git for consistency purposes, please? Other than that, your PR looks good to me.

[rwhitby]

Sorry, I did not intend that second commit to be part of this pull request. I will move it to a different branch so that it can be a separate pull request (which will have the correct submodule path after the pull request on nextpnr-xilinx has been merged).

[rwhitby]

I have removed the offending additional commit, so this simple 1 line change can now be merged here at your convenience.