`build_env` is assumed to be a certain trivial environment, e.g. a
singleton search path.
An environment in general is either empty, contain one or more search
paths separated by a colon.
It seems that the intent was to set the `build_shell` first as a
prepended path in the managed environment then extend via the
`build_env` parts.
This fixes a usecase when the `BUILD_TEST_ENV` is non-trivial.
Change-Id: If5b8ab976d867a57ce0b8d29255f64695e30a8b2
Signed-off-by: Raito Bezarius <raito@lix.systems>
Raito Bezarius
b730fab286