xen: pass compiler flags via Xen-provided variables
xen: pass compiler flags via Xen-provided variables

Fix the method of passing compiler flags into the Xen build, which is
needed to fix compilation of hvmloader, a 32-bit firmware binary that is
required for Xen to be able to run HVM-mode guest VMs. It must not be
compiled with SSE compiler options enabled, so the Xen build clears
CFLAGS, which is a problem with _FORTIFY_SOURCE present in CC because
it must be paired with a compiler optimization flag that was in CFLAGS.
This change fixes the compilation failure that stated
 "_FORTIFY_SOURCE requires compiling with optimization (-O)".

32-bit ARM needs the TUNE_CCARGS to be retained as passed via CC
to ensure that configure is able to generate binaries for the
correct ABI, so is handled as a separate case.

Signed-off-by: Christopher Clark <92b288ff708f124106db1be7360ea774d4cfcb08@baesystems.com>
Reviewed-by: Jason Andryuk <8558cf2f125c210e58f86c566cb85d5e97963455@gmail.com>
Signed-off-by: Bruce Ashfield <284cc737d174a260eec2a2a6324a304f84b1ae0f@gmail.com>

lgirdk/meta-virtualization,lgirdk/meta-virtualization,lgirdk/meta-virtualization,lgirdk/meta-virtualization,lgirdk/meta-virtualization