package/Makefile.in: adjust LDFLAGS for elf2flt

package/Makefile.in: adjust LDFLAGS for elf2flt

So far, our LDFLAGS for the BR2_BINFMT_FLAT case were only used on
Blackfin. However, passing -elf2flt in LDFLAGS is wrong. Indeed,
LDFLAGS are not linker flags, but flags passed to the compiler when
linking.

If you pass -elf2flt to the compiler when linking, it is understood as
"-e lf2flt", i.e "the entry point is named lf2flt", which isn't
exactly the intention. We in fact need to pass -Wl,-elf2flt in LDFLAGS
as well, so that the compiler passes -elf2flt down to the linker.

For some reason, this option does not cause an issue with the Blackfin
toolchain, but it does with either a Buildroot toolchain for Cortex-M
or an OSELAS toolchain for Cortex-M. We have verified that passing
-Wl,-elf2flt continues to work with the Blackfin toolchain.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>