Disable linking libgcc.a with --whole-archive option

This patch disables linking libgcc.a library with
--whole-archive in order to make resulting loader-stripped.elf
2.5 MB smaller. The libgcc.a contains number of functions and huge tables
of numbers that are part of Decimal Float Library
(https://gcc.gnu.org/onlinedocs/gccint/Decimal-float-library-routines.html#Decimal-float-library-routines),
which are not used by OSv kernel.

Any potential side-effects caused by this patch have been
tested against almost 20 different apps including
java, python, golang, rust, MySQL and redis and no
issues have been found.

Size of kernel (ROFS version) before this patch:
9.2M	loader-stripped.elf
6.2M	lzloader.elf (33% reduction)

Size of kernel (ROFS version) after this patch:
6.7M	loader-stripped.elf
3.9M	lzloader.elf (42% reduction)

These are related patches:
c9e61d4
be56532

Signed-off-by: Waldemar Kozaczuk <[email protected]>
Message-Id: <[email protected]>

Makefile

@@ -1869,9 +1869,9 @@ $(out)/loader.elf: $(stage1_targets) arch/$(arch)/loader.ld $(out)/bootfs.o
 		-Bdynamic --export-dynamic --eh-frame-hdr --enable-new-dtags \
 	    $(^:%.ld=-T %.ld) \
 	    --whole-archive \
-	      $(libstdc++.a) $(libgcc.a) $(libgcc_eh.a) \
+	      $(libstdc++.a) $(libgcc_eh.a) \
 	      $(boost-libs) \
-	    --no-whole-archive, \
+	    --no-whole-archive $(libgcc.a), \
 		LINK loader.elf)
 	@# Build libosv.so matching this loader.elf. This is not a separate
 	@# rule because that caused bug #545.