x86, powerpc: Remove -funit-at-a-time compiler option entirely

GCC 4.6 manual says:

  -funit-at-a-time
    This option is left for compatibility reasons. -funit-at-a-time has
    no effect, while -fno-unit-at-a-time implies -fno-toplevel-reorder
    and -fno-section-anchors. Enabled by default.

Remove it.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Richard Weinberger <richard@sigma-star.at>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/1541990120-9643-3-git-send-email-yamada.masahiro@socionext.com

arch/powerpc/Makefile

@@ -228,10 +228,6 @@ KBUILD_CFLAGS += $(call cc-option,-mno-vsx)
 KBUILD_CFLAGS += $(call cc-option,-mno-spe)
 KBUILD_CFLAGS += $(call cc-option,-mspe=no)
 
-# Enable unit-at-a-time mode when possible. It shrinks the
-# kernel considerably.
-KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
-
 # FIXME: the module load should be taught about the additional relocs
 # generated by this.
 # revert to pre-gcc-4.4 behaviour of .eh_frame

arch/x86/Makefile

@@ -130,10 +130,6 @@ else
 
         KBUILD_CFLAGS += -mno-red-zone
         KBUILD_CFLAGS += -mcmodel=kernel
-
-        # -funit-at-a-time shrinks the kernel .text considerably
-        # unfortunately it makes reading oopses harder.
-        KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
 endif
 
 ifdef CONFIG_X86_X32

arch/x86/Makefile.um

@@ -26,9 +26,6 @@ cflags-y += $(call cc-option,-mpreferred-stack-boundary=2)
 # an unresolved reference.
 cflags-y += -ffreestanding
 
-# gcc 4.3.0 needs -funit-at-a-time for extern inline functions.
-KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
-
 KBUILD_CFLAGS += $(cflags-y)
 
 else
@@ -50,6 +47,4 @@ ELF_FORMAT := elf64-x86-64
 LINK-$(CONFIG_LD_SCRIPT_DYN) += -Wl,-rpath,/lib64
 LINK-y += -m64
 
-# Do unit-at-a-time unconditionally on x86_64, following the host
-KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
 endif