Since x86_64-zephyr-elf is a multi-lib toolchain, m32/m64
need to be specified for the compiler to return the correct
library path when queried (e.g. --print-libgcc-file-name).
This affects the compile check done by CMake. Without these
flags, the compiler returns incorrect toolchain path (e.g.
requiring 64-bit libraries but returning 32-bit library path).
This also affects compiler flag checks for "-lstdc++". Incorrect
library path results in error when checking for "-lstdc++", and
this flag will not be used for the build. This results in
undefined references when compiling C++ code.
This creates target_x86.cmake to add the necessary flags for
CMake to use. The target_x86_64.cmake is also created to
mirror the same change.
Also removing the -m32 flags for host-gcc since we are not
building x86 targets with the host-gcc compiler.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
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