build: Add and build OpenFST submodule.

.gitmodules

@@ -59,3 +59,6 @@
 	path = piper
 	url = https://github.com/shaunren/piper.git
 	branch = library
+[submodule "openfst"]
+	path = openfst
+	url = https://github.com/alphacep/openfst

Makefile.in

@@ -400,6 +400,47 @@ $(OBJ)/.piper-x86_64-post-build:
 	cp -a $(PIPER_x86_64_DST)/{espeak-ng-data,libtashkeel_model.ort} $(DST_DIR)/share/
 	touch $@
 
+##
+## openfst
+##
+
+OPENFST_SOURCE_ARGS = \
+  --include src/include/fst/config.h.in \
+  --exclude aclocal.m4 \
+  --exclude ar-lib \
+  --exclude autom4te.cache \
+  --exclude compile \
+  --exclude config.guess \
+  --exclude config.h.in \
+  --exclude config.sub \
+  --exclude configure \
+  --exclude depcomp \
+  --exclude install-sh \
+  --exclude ltmain.sh \
+  --exclude m4/libtool.m4 \
+  --exclude m4/ltoptions.m4 \
+  --exclude m4/ltsugar.m4 \
+  --exclude m4/ltversion.m4 \
+  --exclude m4/lt~obsolete.m4 \
+  --exclude Makefile.in \
+  --exclude missing \
+  --exclude test-driver \
+
+OPENFST_CONFIGURE_ARGS = \
+  --enable-silent-rules \
+  --enable-static \
+  --disable-shared \
+  --enable-far \
+  --enable-ngram-fsts \
+  --enable-lookahead-fsts \
+  --with-pic \
+  --disable-bin \
+
+$(eval $(call rules-source,openfst,$(SRCDIR)/openfst))
+$(eval $(call rules-configure,openfst,i386,unix))
+$(eval $(call rules-configure,openfst,x86_64,unix))
+
+
 ##
 ## wine
 ##

openfst

@@ -0,0 +1 @@
+Subproject commit 7dfd808194105162f20084bb4d8e4ee4b65266d5