s390/decompressor: fix misaligned symbol build error

Nathan Chancellor reported a kernel build error on Fedora 39:

$ clang --version | head -1
clang version 16.0.5 (Fedora 16.0.5-1.fc39)

$ s390x-linux-gnu-ld --version | head -1
GNU ld version 2.40-1.fc39

$ make -skj"$(nproc)" ARCH=s390 CC=clang CROSS_COMPILE=s390x-linux-gnu- olddefconfig all
s390x-linux-gnu-ld: arch/s390/boot/startup.o(.text+0x5b4): misaligned symbol `_decompressor_end' (0x35b0f) for relocation R_390_PC32DBL
make[3]: *** [.../arch/s390/boot/Makefile:78: arch/s390/boot/vmlinux] Error 1

It turned out that the problem with misaligned symbols on s390 was fixed
with commit 80ddf5c ("s390: always build relocatable kernel") for the
kernel image, but did not take into account that the decompressor uses its
own set of CFLAGS, which come without -fPIE.

Add the -fPIE flag also to the decompresser CFLAGS to fix this.

Reported-by: Nathan Chancellor <[email protected]>
Tested-by: Nathan Chancellor <[email protected]>
Reported-by: CKI <[email protected]>
Suggested-by: Ulrich Weigand <[email protected]>
Link: ClangBuiltLinux#1747
Link: https://lore.kernel.org/[email protected]/
Link: https://lore.kernel.org/r/[email protected]
Cc: <[email protected]>
Signed-off-by: Heiko Carstens <[email protected]>
Signed-off-by: Alexander Gordeev <[email protected]>

Author: hcahca

arch/s390/Makefile

@@ -27,6 +27,7 @@ KBUILD_CFLAGS_DECOMPRESSOR += -fno-delete-null-pointer-checks -msoft-float -mbac
 KBUILD_CFLAGS_DECOMPRESSOR += -fno-asynchronous-unwind-tables
 KBUILD_CFLAGS_DECOMPRESSOR += -ffreestanding
 KBUILD_CFLAGS_DECOMPRESSOR += -fno-stack-protector
+KBUILD_CFLAGS_DECOMPRESSOR += -fPIE
 KBUILD_CFLAGS_DECOMPRESSOR += $(call cc-disable-warning, address-of-packed-member)
 KBUILD_CFLAGS_DECOMPRESSOR += $(if $(CONFIG_DEBUG_INFO),-g)
 KBUILD_CFLAGS_DECOMPRESSOR += $(if $(CONFIG_DEBUG_INFO_DWARF4), $(call cc-option, -gdwarf-4,))