artiq_flash: explicitly pass path within conda env to openocd datarootdir.

By default, openocd searches for scripts in DATAROOTDIR/openocd/scripts.
This of course makes it not relocatable. Conda has a flag to try to
detect and fix such hardcoded paths, but it does not work on openocd
(likely because the .rodata contains an already concatenated path,
which cannot be padded with zeroes from the right).

So, we pass the path explicitly instead.

artiq/frontend/artiq_flash.py

@@ -5,6 +5,7 @@ import argparse
 import os
 import subprocess
 import tempfile
+import site
 
 from artiq import __artiq_dir__ as artiq_dir
 from artiq.frontend.bit2bin import bit2bin
@@ -76,6 +77,12 @@ def main():
         raise SystemExit("Binaries directory '{}' does not exist"
                          .format(opts.dir))
 
+    conda_prefix_path = site.getsitepackages()[0]
+    if os.name == "nt":
+        scripts_path = os.path.join(conda_prefix_path, "Library", "share", "openocd", "scripts")
+    else:
+        scripts_path = os.path.join(conda_prefix_path, "share", "openocd", "scripts")
+
     conv = False
 
     prog = []
@@ -124,6 +131,7 @@ def main():
             bit2bin(bit, bin_handle)
         subprocess.check_call([
             "openocd",
+            "-s", scripts_path,
             "-f", os.path.join("board", opts.target + ".cfg"),
             "-c", "; ".join(prog),
         ])