buildenv: Turn off native architecture builds
buildenv: Turn off native architecture builds

The compiler option -march=native instructs the compiler to auto-optimize
the code for the current build architecture. This is fine for building
and using locally, but contraproductive when generating binary packages.

This commit replaces -march=native with $(SIMD_FLAGS), which contains a
collection of supported SIMD options, so we won't loose the SSE support.

Change-Id: I3df4b8db9692016115edbe2247beeec090715687

osmocom/osmo-trx,osmocom/osmo-trx,ttsou/osmo-trx,ttsou/osmo-trx,osmocom/osmo-trx,ttsou/osmo-trx,ttsou/osmo-trx,osmocom/osmo-trx