clang.bbclass: Add -pie -fPIE to SECURITY_PIE_CFLAGS explicitly
clang.bbclass: Add -pie -fPIE to SECURITY_PIE_CFLAGS explicitly

gcc in core now is configured with these options but clang
does not have a configuration level knob so we still need to
pass it old way

Signed-off-by: Khem Raj <729d64b6f67515e258459a5f6d20ec88b2caf8df@gmail.com>

kraj/meta-clang,kraj/meta-clang,kraj/meta-clang