compel hgen: use for ARM, kill gen-offsets.sh

I am not quite sure how that happened, but compel hgen was not used for
ARM/ARM64, instead there's a simple version of it, called
gen-offsets.sh. The main difference is, shell script doesn't handle ELF
relocations, which apparently is not (currently?) needed for ARM.

It's bad to maintain two tools for the same functionality, so this
patch kills gen-offsets.sh and related stuff, making compel hgen
working on ARM. ELF relocations are still not handled, this code
is #ifdef-ed out for now and can be fixed to work on ARM later.

This patch also kills some macros and defines that seem obsoleted
now. For example, compel_relocs_apply() is now called unconditionally,
as it handles the trivial case of 0 relocs just fine.

Now, I checked that the blob headers generated by compel hgen and
gen-offsets.h are similar (i.e. generated blob code and values defined
are the same), but haven't done much above that.

Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

Makefile

@@ -176,16 +176,6 @@ include/common/asm: include/common/arch/$(ARCH)/asm
 	$(Q) ln -s ./arch/$(ARCH)/asm $@
 $(VERSION_HEADER): include/common/asm
 
-#
-# piegen tool might be disabled by hands. Don't use it until
-# you know what you're doing.
-ifneq ($(filter ia32 x86 ppc64,$(ARCH)),)
-        ifneq ($(PIEGEN),no)
-                piegen-y := y
-                export piegen-y
-        endif
-endif
-
 #
 # Configure variables.
 export CONFIG_HEADER := criu/include/config.h