pw_env_setup: Better support for 32-bit ARM hosts
pw_env_setup: Better support for 32-bit ARM hosts

The commonly accepted architecture string for 32-bit ARM hosts is
armv6l, so we now use that when bootstrapping from a 32-bit ARM host.

Change-Id: Ia78ccf6c5b0e81d579c9087ca4068cd31939d969
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/58403
Pigweed-Auto-Submit: Rob Mohr <d07614a8a0b466db08f68224f87d738b0f9615cf@google.com>
Reviewed-by: Anthony DiGirolamo <4cc40125edc24ec5bc72df7917ea0b403ee8cebe@google.com>
Commit-Queue: Auto-Submit <14637eda5603879df170705285bf30f5996692f0@pigweed.google.com.iam.gserviceaccount.com>

google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed