Exec: search for executables in the PATH

Using execvp instead of execv. It'll look for the binary in PATH if
the bin_path provided is not an explicit path.

src/nixglhost_wrapper.py

@@ -422,7 +422,7 @@ def exec_binary(bin_path: str, args: List[str]) -> None:
     # The following two env variables are required by our patched libglvnd
     # implementation to figure out what kind of driver the host
     # machine is using.
-    os.execv(bin_path, [bin_path] + args)
+    os.execvp(bin_path, [bin_path] + args)
 
 
 def main(args):