Add missing -lgcc when compiling with ZEPHYR_TOOLCHAIN_VARIANT=host
merely copying some existing code from
'compiler/{clang,gcc}/target.cmake'.
This fixes compilation for the following boards with an x86
microprocessor:
galileo, minnowboard, qemu_x86, qemu_x86_nommu, up_squared,
up_squared_sbl
Compilation of the following boards with an X86_IAMCU microcontroller
still fail with a "cannot find -lgcc" error:
arduino_101, qemu_x86_iamcu, quark_d2000_crb, quark_se_c1000_devboard,
tinytile
This is _not_ a regression because these boards _already_ failed with
"undefined reference to __udivdi3" and other libgcc symbols.
Signed-off-by: Marc Herbert <marc.herbert@intel.com>