ARM32 configury changes, with no FPU as a default

[Matthias Klose]

Starting with GCC 8, the configury allows to encode extra features into the
architecture string. Debian and Ubuntu's armhf (hard float) architecture is
configured with

  --with-arch=armv7-a --with-fpu=vfpv3-d16

and now should be configured with

  --with-arch=armv7-a+fp

The --with-fpu configure option is deprecated.  The problem with this approach
is that there is no default for the fpu setting, while old compilers silently
pick up the -mfpu from the configured compiler.

This breaks software which explicitly configures things like -march=armv7-a, or
where the architecture string is embedded in the source as an attribute.  So
going from one place in the compiler about configuring the ABI for a distro
arch, this config now moves to some dozen places in different packages.  Not the
thing I would expect.

Richard tells me that the --with-fpu option goes away in some future GCC
version, just asking here how others solved this issue, or are we the only ones
still building for ARM 32bit?

Thanks, Matthias