Compilers generally have /usr/local/include in their default search
path. And if they don't, that has to be considered a local policy
which should not be ignored. The user can always override it by
setting CPPFLAGS.
CPPFLAGS += -DLOGLEVELS='$(LOGLEVELS)'
CPPFLAGS += -DUNAME_RS='"$(uname_rs)"'
CPPFLAGS += -DCC_VERSION='"$(cc_version)"'
-CPPFLAGS += -I/usr/local/include
CPPFLAGS += -I$(lls_suite_dir)
CPPFLAGS += -I$(yy_build_dir)
CPPFLAGS += $(lopsub_cppflags)