procmail: Use build ldflags when invoking native compile/link
Some older compilers do not support security flags like -fstack-protector=strong
and if we do not set this then it will use the target flags to pass here
which will fail with gcc < 5.x, especially a problem building distros with
security flags on host with 4.x gcc e.g. ubuntu 14.04
Signed-off-by: Khem Raj <raj.khem@gmail.com>