[Bug 1939379] Re: ARM kernel builds fail with GCC 11

[dann frazier]

Yeah, I think what's going on is that - due to the above change - gcc-11
no longer enables an FPU independently of the selected arch. The FPU is
only enabled because the default -march is armv7-a+fp. The kernel build
is overriding GCC's (new) built-in default march to one that does not
have "+fp", so no flags remain to enable the FPU. edk2 does something
similar, and changing it's forced -march from armv7-a to armv7-a+fp
works for me.

** Also affects: gcc-11 (Ubuntu)
   Importance: Undecided
       Status: New

** Changed in: gcc-defaults (Ubuntu)
       Status: New => Invalid

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https://bugs.launchpad.net/bugs/1939379

Title:
  ARM kernel builds fail with GCC 11

Status in gcc-11 package in Ubuntu:
  New
Status in gcc-defaults package in Ubuntu:
  Invalid

Bug description:
  While this might be a kernel build problem (see LP: #1939308) I wanted
  to raise the issue against the toolchain just so we can make sure it's
  *not* a toolchain bug. Basically the following behavior changed from
  gcc 10:

  $ arm-linux-gnueabihf-gcc-10 -march=armv7-a -c -x c /dev/null ; echo $?
  0

  $ arm-linux-gnueabihf-gcc-11 -march=armv7-a -c -x c /dev/null ; echo $?
  cc1: error: ‘-mfloat-abi=hard’: selected architecture lacks an FPU
  1

  Presumably the GCC 11 hard-float compiler now enforces the default
  config --with-float=hard?

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