tools/ci.sh: Extend Arm testing to include hardfp targets.

This commit lets CI extend the testing scope of the QEMU Arm target, by
letting it perform the usual battery of tests (interpreter and natmods)
also on hardfp targets.

The default board for Arm testing lacks hardware floating point support,
so natmods weren't tested in that specific configuration.  With the
introduction of the "MPS_AN500" QEMU target, now this is made possible
as said board emulates a Cortex-M7 machine with a single- and
double-precision floating point unit.

To reduce the impact on build times, the "ci_qemu_build_arm_thumb" CI
step was split in two: "ci_qemu_build_arm_thumb_softfp" and
"ci_qemu_build_arm_thumb_hardfp" - so hopefully those can run in
parallel whenever possible.

Signed-off-by: Alessandro Gatti <a.gatti@frob.it>

.github/workflows/ports_qemu.yml

@@ -26,7 +26,8 @@ jobs:
         ci_func:  # names are functions in ci.sh
           - bigendian
           - sabrelite
-          - thumb
+          - thumb_softfp
+          - thumb_hardfp
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v5