efibootmgr: Pass correct flags to compiler from pkg-config
efivar.h is in usr/include/efirvar directory so it should be
added to include search path via -I to compiler cmdline to fix
make[1]: *** No rule to make target 'efivar.h', needed by 'efibootmgr.o'. Stop.
| make[1]: *** Waiting for unfinished jobs....
When running clang to generate dependencies -MM -MG -MF it still
parses the compile unit and complains if certain header is not found
where as gcc does not do that, hence the compile error is only seen
when compiling with clang.
Signed-off-by: Khem Raj <raj.khem@gmail.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
