...by separating out CPPFLAGS and CXXFLAGS.
#DEBUG_SUFFIX:=--define-variable=suffix=_d
mod_LTLIBRARIES = mod_opal.la
mod_opal_la_SOURCES = mod_opal.cpp
-mod_opal_la_CFLAGS = $(AM_CFLAGS) $(shell PKG_CONFIG_PATH=$(PKG_CONFIG_PATH):$(PKG_DIR) pkg-config opal $(DEBUG_SUFFIX) --cflags)
+mod_opal_la_CPPFLAGS = $(AM_CPPFLAGS) $(shell PKG_CONFIG_PATH=$(PKG_CONFIG_PATH):$(PKG_DIR) pkg-config opal $(DEBUG_SUFFIX) --cflags | sed 's/-[^ID][^ ]*//g')
+mod_opal_la_CXXFLAGS = $(AM_CXXFLAGS) $(shell PKG_CONFIG_PATH=$(PKG_CONFIG_PATH):$(PKG_DIR) pkg-config opal $(DEBUG_SUFFIX) --cflags | sed 's/-[ID][^ ]*//g')
mod_opal_la_LIBADD = $(switch_builddir)/libfreeswitch.la
mod_opal_la_LDFLAGS = -avoid-version -module -no-undefined -shared $(shell pkg-config opal $(DEBUG_SUFFIX) --libs)