Remove unused Android.mk under contexthub/firmware/os
The module names for these Android.mk files are
`libnanohub_bl_cortexm4`, `libnanohub_os_cortexm4`,
`libnanohub_os_x86`, `libnanohub_os_native`, `libnanohub_bl_stm32`, and
`libnanohub_os_stm32`.
After verification, these modules cannot build any targets in Android
because they all ultimately call $(BUILD_AUX_STATIC_LIBRARY), which has
been deprecated in Android.
(Reference: build/make/core/deprecation.mk).
Furthermore, since these modules are not dependencies for any other
targets, it should be safe to remove them.
Bug: 339564655
Bug: 309902275
Test: N/A
Change-Id: I0e3d52b035e24313d49bf9ef73be13d38f6061d7
4 files changed
