ipsecbuild: force CC=cc

This will override use of scan-build for the ipsec-mb build,
since ipsec-mb has scan-build errors and there's no other easy
way to skip ipsec-mb as part of the scan-build process.

Signed-off-by: Jim Harris <james.r.harris@intel.com>
Change-Id: I531d84bcc07a1c1c80f41e20d1026f6f6af0bf28

Reviewed-on: https://review.gerrithub.io/c/442115


Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-by: Ziye Yang <optimistyzy@gmail.com>
Reviewed-by: Shuhei Matsumoto <shuhei.matsumoto.xt@hitachi.com>
Reviewed-by: Changpeng Liu <changpeng.liu@intel.com>
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Chandler-Test-Pool: SPDK Automated Test System <sys_sgsw@intel.com>